Method for producing oxide particles with controlled color characteristics, oxide particles, and coating or film-like composition comprising the same

ABSTRACT

An object of the present invention is to provide a method for producing oxide particles with controlled color characteristics and to provide oxide particles with controlled color characteristics. The present invention provides a method for producing oxide particles, comprising controlling color characteristics of the oxide particles by controlling the ratio of M-OH bonds, the binding of one or more different elements (M) other than oxygen or hydrogen with hydroxyl group (OH), in oxide particles selected from metal oxide particles and metalloid oxide particles. According to the present invention, oxide particles having controlled color characteristics of any one of reflectance, transmittance, molar absorption coefficient, hue, or color saturation can be provided by controlling the percentage of the M-OH bonds contained in metal oxide particles or metalloid oxide particles.

TECHNICAL FIELD

The present invention relates to a method for producing oxide particleswith controlled color characteristics, oxide particles, and a coating orfilm-like composition comprising the oxide particles.

BACKGROUND ART

Oxide particles have characteristic features, such as UV-absorptionproperties and near infrared ray reflection properties, which can bechanged depending on the selection of a type of metal or metalloidelement contained in the oxide particles. Thus, the oxide particles havebeen used in a wide range of fields, including cosmetics, such assunscreen agents, lipsticks, and foundations; building materials, suchas materials for exterior walls and signboards; or paints used forvehicles and glasses. Furthermore, when the intended use of oxideparticles is of being applied to the human body, like cosmetics, theproperties of beauty, texture, and safety are extremely demanded. In thecase of using oxide particles in materials, such as materials forexterior walls and signboards or paints used for vehicles or the like,the demand for design properties, such as vividness and color aestheticappearance, is also very high.

For this reason, there have been proposed a method for enhancing theproperties of oxide, such as iron oxide and zinc oxide, including colorcharacteristics, UV-absorption properties, and infrared ray reflectionproperties, by the process of atomizing the oxide (See, for example,Patent Literature 1 and Patent Literature 2) or the process of producingoxide using a plurality of elements other than iron or zinc (see, forexample, Patent Literature 3 and Patent Literature 4).

However, although the transparency of fine particle dispersion can beimproved by atomization, it is difficult to control their reflectance,transmission/absorption properties, color characteristics including hueand color saturation, and the like. In a complex oxide formation,furthermore, the properties of oxide largely change depending on thekinds of metals to be combined, causing in particular a difficulty ofcontrolling the color characteristics of the oxide. These factstherefore make the properties of oxide particles difficult to bedelicately controlled in a precise manner.

Patent Literatures 5 and 6, in which the inventions thereof aredisclosed by the present inventors, disclose a method for producinguniform oxide nanoparticles by the process of precipitating variousnanoparticles of an iron oxide and the like between two processingsurfaces being capable of approaching to and separating from each otherand rotating relative to each other. However, these patent literaturesdo not describe the method for manufacturing oxide with the objective ofcontrolling the color characteristics of the oxide. In other words,Patent Literature 5 describes the separate formation of oxide andhydroxide, while Patent Literature 6 describes the manufacture ofuniform oxide.

CITATION LIST Patent Literature

Patent Literature 1: JP 2009-263547

Patent Literature 2: WO 1998/026011

Patent Literature 3: JP 2010-530448

Patent Literature 4: JP 2013-249393

Patent Literature 5: JP 4868558

Patent Literature 6: WO 2009/008393

SUMMARY OF THE INVENTION Technical Problem

In light of such circumstances, an object of the present invention is toprovide a method for producing oxide particles with controlled colorcharacteristics, and to provide oxide particles with controlled colorcharacteristics. That is, the object is to control the colorcharacteristics by controlling the amount of hydroxyl groups containedin the oxide for the purpose of maximally improving the originalproperties of the oxide and compensating for such properties. The ratioand morphology of M-OH bonds contained in oxides vary depending on theprocess of producing the oxides and any environmental change after theproduction. An object is to control the reflectance of oxide in anear-infrared region of 780 nm to 2500 nm in wavelength. Also, an objectis to control the reflectance, transmittance, hue, or color saturationof oxide in a visible region of 380 nm to 780 nm in wavelength.Furthermore, an object of the present invention is to controlreflectance or molar absorption coefficient in a visible region of 190nm to 380 nm. The present inventors have completed the present inventionby finding the relevance of the ratio of M-OH bonds contained in oxideparticles and the transmission, absorption, reflection properties andhue or color saturation of the oxide particles, such as iron oxideparticles, zinc oxide particles, cerium oxide particles, andcobalt-zinc-complex oxide particles, and also found that the colorcharacteristics of oxide particles can be improved by controlling theratio of M-OH bonds contained in oxide particles. In view of the abovecircumstances, an object of the present invention is to provide acoating or film-like composition containing oxide particles havingcontrolled color characteristics.

Solution to the Problem

The present inventors have found that the ratio of M-OH bonds containedin metal oxide particles or metalloid oxide particles (hereinafter,collectively referred to as “oxide particles”) has relevance to thetransmission properties, absorption properties, reflection properties,color characteristics such as hue or color saturation or the like ofoxide particles, and as a result, have completed the present invention.

More specifically, the present invention is a method for producing oxideparticles, the process featuring that the color characteristics of theoxide particles are controlled by controlling the ratio of M-OH bondswhich are the bonding of one or two or more elements (M) other thanoxygen or hydrogen with hydroxyl groups (OH), contained in oxideparticles selected from metal oxide particles and metalloid oxideparticles.

In the present invention, preferably, the ratio of M-OH bonds asdescribed above may be calculated by waveform separation of peaksderived from the above oxide particles at wavenumbers of 100 cm⁻¹ to1250 cm⁻¹ in an infrared absorption spectrum. The color characteristicsare controlled preferably by controlling an area ratio of thewaveform-separated peak derived from the M-OH bonds to the total area ofeach waveform-separated peak.

In the present invention, preferably, the color characteristics of theoxide particles may be any one of reflectance, transmittance, molarabsorption coefficient, hue, or color saturation.

In the present invention, preferably, the ratio of M-OH bonds containedin the oxide particles is controlled by modifying a functional groupcontained in the oxide particles. In the present invention, preferably,the modification of the functional group is any one of an additionreaction, an elimination reaction, a dehydration reaction, and adisplacement reaction. In the present invention, preferably, themodification of the functional group is esterification.

In the present invention, preferably, the ratio of M-OH bonds iscontrolled by a state of a dispersion in which the oxide particles aredispersed in a dispersion medium. In the present invention, preferably,the dispersion is in the form of a coating film, and the colorcharacteristics of the oxide particles are controlled by subjecting thecoating film-like dispersion to a heat treatment.

In the present invention, preferably, the ratio of M-OH bond iscontrolled using a dispersion-improving apparatus comprising a removalunit with a membrane filter.

In the present invention, preferably, the oxide particles are oxideparticles in which at least a part of the surface of a single oxideparticle or at least a part of the surface of an aggregate formed byaggregation of a plurality of oxide particles is coated with a siliconcompound.

In the present invention, preferably, the particle diameter of the oxideparticle or the aggregate of oxide particle is 1 nm or more and 50 nm orless.

The present invention may be embodied as a method for producing oxideparticles, wherein the average reflectance for light rays at wavelengthsof 780 nm to 2500 nm is controlled to be high by controlling the arearatio of the waveform-separated peak derived from the M-OH bonds to thetotal area of each waveform-separated peak to be low.

The present invention may be embodied as a method for producing oxideparticles, wherein an average molar absorption coefficient for lightrays at wavelengths of 190 nm to 380 nm is controlled to be high bycontrolling the area ratio of the waveform-separated peak derived fromthe M-OH bonds to the total area of each waveform-separated peak to below.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is iron oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 8% or more and 14.5% or less,and the average reflectance of the oxide particles for light rays atwavelengths of 780 nm to 2500 nm is 50% or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is iron oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 10% or more and 15% or less,and the maximum reflectance of the oxide particles for light rays at awavelength of 400 nm to 620 nm is 18% or less.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is iron oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 9.5% or more and 15% or less,and the average reflectance of the oxide particles for light rays atwavelengths of 620 nm to 750 nm is 22% or less.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is iron oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 8% or more and 15% or less,and hue H (=b*/a*) in an L*a*b* colorimetric system is in the range of0.5 to 0.9.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is iron oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 9% or more and 15% or less,and, in a transmission spectrum of a dispersion in which the oxideparticles are dispersed in a dispersion medium, the transmittance forlight rays at a wavelength of 380 nm is 5% or less and the transmittancefor light rays at a wavelength of 600 nm is 80% or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is iron oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 9% or more and 15% or less,and, in a dispersion in which the oxide particles are dispersed in adispersion medium, an average molar absorption coefficient for lightrays at wavelengths of 190 nm to 380 nm is 2200 L/(mol·cm) or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is iron oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the oxide particlesincludes ester bonds, the ratio of M-OH bonds contained in the oxideparticles is 9% or more and 13% or less, and the average reflectance ofthe oxide particles for light rays at wavelengths of 780 nm to 2500 nmis 50% or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is iron oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 8% or more and 9.3% or less,or 13.3% or more and 15% or less, and the average reflectance of theoxide particles for light rays at wavelengths of 620 nm to 750 nm ishigher than 22%.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is zinc oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 30% or more and 39% or less,and the average reflectance of the oxide particles for light rays atwavelengths of 780 nm to 2500 nm is 72% or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is zinc oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 30% or more and 36% or less,and a wavelength at which the reflectance of the oxide particles is 15%is 375 nm or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is zinc oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 38% or more and 42% or less,and an average reflectance for light rays at wavelengths of 380 nm to780 nm is 86% or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is zinc oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 31% or more and 39% or less,and a color saturation C(=((a*)²+(b*)²)^(1/2)) in an L*a*b* colorimetricsystem is in the range of 0.5 to 13.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is zinc oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 38% or more and 42% or less,and, in a transmission spectrum of a dispersion in which the oxideparticles are dispersed in a dispersion medium, the transmittance forlight rays at a wavelength of 340 nm is 10% or less and thetransmittance for light rays at wavelengths of 380 nm to 780 nm is 92%or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is zinc oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 30% or more and 36% or less,and, in a transmission spectrum of a dispersion in which the oxideparticles are dispersed in a dispersion medium, a wavelength at whichthe reflectance of the oxide particles becomes 15% is 365 nm or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is zinc oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 30% or more and 42% or less,and, in a dispersion in which the oxide particles are dispersed in adispersion medium, an average molar absorption coefficient for lightrays at wavelengths of 200 nm to 380 nm is 700 L/(mol·cm) or more.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is zinc oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 31% or more and 39% or less, acolor saturation C(=((a*)²+(b*)²)^(1/2)) in an L*a*b* colorimetricsystem is in the range of 0.5 to 13, and an L* value in the L*a*b*colorimetric system is in the range of 95 to 97.

Furthermore, the present invention is silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is cerium oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, the ratio of M-OHbonds contained in the oxide particles is 25% or more and 35% or less,and, in a dispersion in which the oxide particles are dispersed in adispersion medium, an average molar absorption coefficient for lightrays at wavelengths of 200 nm to 380 nm is 4000 L/(mol·cm) or more.

Furthermore, in the present invention, preferably, oxide particleshaving the controlled ratio of M-OH bonds contained in the oxideparticles are oxide particles in which at least a part of the surface ofa single oxide particle or at least a part of the surface of anaggregate formed by aggregation of a plurality of oxide particles iscoated with a silicon compound, and the particle diameter of the oxideparticle or the aggregate of oxide particle is 1 nm or more and 50 nm orless.

Furthermore, the present invention may be embodied as one in which thesilicon compound comprises amorphous silicon oxide.

Furthermore, the present invention is preferably oxide particlescomprising iron oxide, wherein the ratio of M-OH bonds contained in theoxide particles is 1.5% or more and 7.5% or less, and, in a dispersionin which the oxide particles are dispersed in a dispersion medium, anaverage molar absorption coefficient for light rays at wavelengths of190 nm to 380 nm is 1000 L/(mol·cm) or more.

Furthermore, the present invention is preferably oxide particlescomprising iron oxide, wherein the ratio of M-OH bonds contained in theoxide particles is 1.5% or more and 7.5% or less, and the averagereflectance of the oxide particles for light rays at wavelengths of 780nm to 2500 nm is 55% or more.

Furthermore, the present invention is preferably oxide particlescomprising cerium oxide, wherein the ratio of M-OH bonds contained inthe oxide particles is 12.5% or less, and an average molar absorptioncoefficient for light rays at wavelengths of 200 nm to 380 nm is 3500L/(mol·cm) or more.

Furthermore, the present invention is preferably oxide particlescomprising cerium oxide, wherein the ratio of M-OH bonds contained inthe oxide particles is 11% or less, and in a dispersion in which theoxide particles are dispersed in a dispersion medium, an average molarabsorption coefficient for light rays at wavelengths of 200 nm to 380 nmis 4000 L/(mol·cm) or more.

Furthermore, the present invention is preferably oxide particlescomposed of cobalt zinc complex oxide, wherein the ratio of M-OH bondscontained in the oxide particles is 0.5% or more and 20% or less, and anaverage molar absorption coefficient for light rays at wavelengths of200 nm to 380 nm is 700 L/(mol·cm) or more.

Furthermore, the present invention is preferably oxide particlescomposed of silicon-cobalt-zinc-complex oxide, wherein the ratio of M-OHbonds contained in the oxide particles is 13% or more and 33% or less,and in a dispersion in which the oxide particles are dispersed in adispersion medium, an average molar absorption coefficient for lightrays at wavelengths of 200 nm to 380 nm is 800 L/(mol·cm) or more.

Furthermore, the present invention is preferably oxide particlescomposed of any one of the iron oxide, the cerium oxide, the cobalt zinccomplex oxide, or the silicon-cobalt-zinc-complex oxide, wherein theprimary particle diameter of the oxide particles is 100 nm or less.

Furthermore, the present invention is preferably oxide particlescomprising zinc oxide particles having a primary particle diameter of 50nm or less, wherein the ratio of M-OH bonds contained in the oxideparticles is 12% or less, and in a dispersion in which the oxideparticles are dispersed in a dispersion medium, an average molarabsorption coefficient for light rays at wavelengths of 200 nm to 380 nmis 500 L/(mol·cm) or more.

Furthermore, the present invention is preferably oxide particlescomprising zinc oxide particles having a primary particle diameter of 50nm or less, wherein the ratio of M-OH bonds contained in the oxideparticles is 11.2% or less, and in a dispersion in which the oxideparticles are dispersed in a dispersion medium, an average molarabsorption coefficient for light rays at wavelengths of 200 nm to 380 nmis 650 L/(mol·cm) or more.

Furthermore, the present invention is preferably oxide particlescomprising zinc oxide particles having a primary particle diameter of 50nm or less, wherein the ratio of M-OH bonds contained in the oxideparticles is 12% or less, and the average reflectance of the oxideparticles for light rays at a wavelength of 780 nm to 2500 nm is 65% ormore.

Furthermore, the present invention is preferably oxide particlescomprising zinc oxide particles having a primary particle diameter of 50nm or less, wherein the ratio of M-OH bonds contained in the oxideparticles is 12% or less, and in a dispersion in which the oxideparticles are dispersed in a dispersion medium, a transmittance forlight rays at a wavelength of 330 nm is 10% or less, and an averagereflectance for light rays at wavelengths of 380 nm to 780 nm is 90% ormore.

Furthermore, the present invention is the haze value of an oxidedispersion obtained by dispersing the oxide particles in the dispersionmedium is 1% or less.

Furthermore, the present invention may be embodied as a coating orfilm-like oxide composition comprising the oxide particles having thecontrolled ratio of M-OH bonds.

Advantageous Effects of the Invention

According to the present invention, oxide particles having controlledcolor characteristics of any one of reflectance, transmittance, molarabsorption coefficient, hue, or color saturation can be provided bycontrolling the ratio of M-OH bonds contained in metal oxide particlesor metalloid oxide particles. The control of the ratio of M-OH bondsallows the color characteristics of oxide particles to be strictlycontrolled, so that the design of a composition can be easily performedmore accurately than the conventional one to deal with the diversifyingapplication and target properties of oxide particles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the results of STEM mapping of siliconcompound-coated iron oxide particles in which the surface of iron oxideparticles were coated with a silicon compound, obtained in Example 1-5of the present invention.

FIG. 2 is a diagram illustrating the results of a line analysis ofsilicon compound-coated iron oxide particles in which the surface ofiron oxide particles were coated with a silicon compound, obtained inExample 1-5 of the present invention.

FIG. 3 is a diagram illustrating the results of STEM-mapping of siliconcompound-coated iron oxide particles in which a part of the surface ofiron oxide particles obtained in Example 1 of the present invention iscoated with a silicon compound.

FIG. 4 is a diagram illustrating the results of a line analysis ofsilicon compound-coated iron oxide particles in which a part of thesurface of iron oxide particles obtained in Example 1 of the presentinvention is coated with a silicon compound.

FIG. 5 is a diagram illustrating the results of IR measurement ofsilicon compound-coated iron oxide particles obtained in Example 1 andExample 1-5 of the present invention.

FIG. 6 is a diagram illustrating the results of waveform separation of aregion at wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹ in the IR-measurementresults of silicon compound-coated iron oxide particles obtained inExample 1 of the present invention.

FIG. 7 is a diagram illustrating the results of waveform separation ofthe IR-measurement results of silicon compound-coated iron oxideparticles obtained in Example 1-5 of the present invention in a regionat wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹.

FIG. 8 is a diagram illustrating the results of XRD measurement ofsilicon compound-coated iron oxide particles obtained in Example 1-5 ofthe present invention.

FIG. 9 is a diagram illustrating the results of reflection-spectrummeasurement of silicon compound-coated iron oxide particles for lightrays at wavelengths of 200 nm to 2500 nm, the oxide particles beingobtained in the examples of the present invention.

FIG. 10 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm for the ratio of M-OHbonds contained in silicon compound-coated iron oxide particles obtainedin the examples of the present invention.

FIG. 11 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm for the ratio of M-OHbonds contained in silicon compound-coated iron oxide particles obtainedin the examples of the present invention where an aqueous dispersion ofsilicon compound-coated iron oxide particles is subjected to a heattreatment.

FIG. 12 is a diagram illustrating the results of the transmissionspectrum measurement of dispersions in which silicon compound-coatediron oxide particles obtained in Example 1 and Example 1-5 and ironoxide particles obtained in Example 4 of the present invention wererespectively dispersed in propylene glycol.

FIG. 13 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm for the ratio of M-OHbonds contained in silicon compound-coated iron oxide particles obtainedin the examples of the present invention.

FIG. 14 is a graphic diagram illustrating the maximum reflectance forlight rays at wavelengths of 400 nm to 620 nm for the ratio of M-OHbonds contained in silicon compound-coated iron oxide particles obtainedin the examples of the present invention.

FIG. 15 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 620 nm to 750 nm for the ratio of M-OHbonds contained in silicon compound-coated iron oxide particles obtainedin the examples of the present invention.

FIG. 16 is a graphic diagram illustrating hue in an L*a*b* colorimetricsystem for the ratio of M-OH bonds contained in silicon compound-coatediron oxide particles obtained in the examples of the present invention.

FIG. 17 is a graphic diagram illustrating the molar absorptioncoefficient of a dispersion medium in which silicon compound-coated ironoxide particles obtained in Example 1 and Example 1-5 of the presentinvention are dispersed in polypropylene glycol and the molar absorptioncoefficient of a dispersion medium in which iron oxide particlesobtained in Example 4 of the present invention is dispersed inpolypropylene glycol.

FIG. 18 is a graphic diagram illustrating the average molar absorptioncoefficient for light rays at wave lengths of 190 nm to 380 nm for adispersion in which silicon compound-coated iron oxide particles aredispersed in propylene glycol with respect to the ratio of M-OH bondscontained in the silicon compound-coated iron oxide particles obtainedin each of Examples 1, 1-3, 1-4, and 1-5.

FIG. 19 is a diagram illustrating the results of reflection spectrummeasurement of silicon compound-coated iron oxide particles for lightrays at wavelengths of 200 nm to 2500 nm, the oxide particles beingobtained in each of Examples 1, 1-9, and 1-10 of the present invention.

FIG. 20 is a diagram illustrating the results of IR measurement ofsilicon compound-coated iron oxide particles obtained in Example 1 andExample 1-9 of the present invention.

FIG. 21 is a diagram illustrating the results of STEM mapping of siliconcompound-coated iron oxide particles in which the surface of zinc oxideparticles were coated with a silicon compound, obtained in Example 2 ofthe present invention.

FIG. 22 is a diagram illustrating the results of a line analysis ofsilicon compound-silicon compound-coated zinc oxide particles in whichthe surface of iron oxide particles were coated with a silicon compound,obtained in Example 2 of the present invention.

FIG. 23 is a diagram illustrating the results of STEM mapping of siliconcompound-coated iron oxide particles in which part of the surface ofzinc oxide particles obtained in Example 2-4 of the present invention iscoated with a silicon compound.

FIG. 24 is a diagram illustrating the results of a line analysis ofsilicon compound-coated iron oxide particles in which part of thesurface of zinc oxide particles obtained in Example 2-4 of the presentinvention is coated with a silicon compound.

FIG. 25 is a diagram illustrating the results of reflection spectrummeasurement of silicon compound-coated zinc oxide particles for lightrays at wavelengths of 200 nm to 2500 nm, the oxide particles beingobtained in the examples of the present invention.

FIG. 26 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm for the ratio of M-OHbonds contained in silicon compound-coated zinc oxide particles obtainedin the examples of the present invention.

FIG. 27 is a graphic diagram illustrating the results of reflectionspectrum measurement for light rays at wavelengths of 200 nm to 780 nmfor the ratio of M-OH bonds contained in silicon compound-coated zincoxide particles obtained in the examples of the present invention.

FIG. 28 is a graphic diagram illustrating color saturation in an L*a*b*colorimetric system for the ratio of M-OH bonds contained in siliconcompound-coated zinc oxide particles obtained in the examples of thepresent invention.

FIG. 29 is a graphic diagram illustrating L* values in an L*a*b*colorimetric system for the ratio of M-OH bonds contained in siliconcompound-coated zinc oxide particles obtained in the examples of thepresent invention.

FIG. 30 is a diagram illustrating the results of the transmissionspectrum measurement of dispersions in which silicon compound-coatediron oxide particles obtained in Examples 2, 2-2, 2-3, and 2-4 and zincoxide particles obtained in Example 5 of the present invention wererespectively dispersed in propylene glycol.

FIG. 31 is a diagram illustrating molar absorption coefficients ofdispersions in which silicon compound-coated iron oxide particlesobtained in Example 1 and Examples 2, 2-2, 2-3, and 2-4 and zinc oxideparticles obtained in Example 5 of the present invention wererespectively dispersed in propylene glycol.

FIG. 32 is a TEM photograph of silicon compound-coated oxide ceriumparticles in which the surface of cerium oxide particles obtained inExample 3 of the present invention is coated with a silicon compound.

FIG. 33 is a diagram illustrating molar absorption coefficients ofdispersions in which silicon compound-coated cerium oxide particleobtained in Example 3 and cerium oxide particle obtained in Example 8 ofthe present invention were respectively dispersed in propylene glycol.

FIG. 34 is a schematic diagram illustrating an apparatus used for themethod for controlling the ratio of M-OH bonds contained in the oxideparticles of the present invention.

FIG. 35 is a diagram illustrating the results of XRD measurement of ironoxide particles obtained in Example 4 of the present invention.

FIG. 36 is a diagram illustrating the results of IR measurement in aregion at wavenumbers of 50 cm⁻¹ to 4000 cm⁻¹ of iron oxide particlesobtained in Example 4 and Example 4-4 of the present invention.

FIG. 37 is a diagram illustrating the results of waveform separation ofthe IR measurement results of silicon compound-coated iron oxideparticles obtained in Example 4 of the present invention in a region atwavenumbers of 100 cm⁻¹ to 1250 cm⁻¹.

FIG. 38 is a diagram illustrating the results of waveform separation ofthe IR measurement results of silicon compound-coated iron oxideparticles obtained in Example 4-4 of the present invention in a regionat wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹.

FIG. 39 is a graphic diagram illustrating a molar absorption coefficientof a dispersion medium in which iron oxide particles obtained in Example4 and Examples 4-2 to 4-4 of the present invention are dispersed inpropylene glycol at measurement wavelengths of 190 nm to 780 nm.

FIG. 40 is a graphic diagram illustrating the average molar absorptioncoefficient for light rays at wave lengths of 190 nm to 380 nm for adispersion in which iron oxide particles are dispersed in propyleneglycol obtained in each of Example 4 and Examples 4-2 to 4-4.

FIG. 41 is a diagram illustrating the results of reflection spectrummeasurement of iron oxide particles for light rays at wavelengths of 200nm to 2500 nm, the oxide particles being obtained in Example 4 andExamples 4-2 to 4-4 of the present invention.

FIG. 42 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm for the ratio of M-OHbonds contained in iron oxide particles obtained in Example 4 andExamples 4-2 to 4-4 of the present invention.

FIG. 43 is a TEM photograph of zinc oxide particles obtained in Example5 of the present invention.

FIG. 44 is a TEM photograph of zinc oxide particles obtained in Example5-4 of the present invention.

FIG. 45 is a diagram illustrating the results of XRD measurement of zincoxide particles obtained in Example 5 of the present invention.

FIG. 46 is a diagram illustrating the results of waveform separation ofthe IR-measurement results of zinc oxide particles obtained in Example 5and Example 5-4 of the present invention in a region at wavenumbers of50 cm⁻¹ to 4000 cm⁻¹.

FIG. 47 is a diagram illustrating the results of waveform separation ofa region at wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹ in the IR measurementresults of zinc oxide particles obtained in Example 5 of the presentinvention.

FIG. 48 is a diagram illustrating the results of waveform separation ofa region at wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹ in the IR measurementresults of zinc oxide particles obtained in Example 5-2 of the presentinvention.

FIG. 49 is a diagram illustrating the results of waveform separation ofa region at wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹ in the IR measurementresults of zinc oxide particles obtained in Example 5-4 of the presentinvention.

FIG. 50 is a graphic diagram illustrating the molar absorptioncoefficient for light rays at measurement wave lengths of 200 nm to 780nm for a dispersion in which zinc oxide particles are dispersed inpropylene glycol obtained in each of Example 5 and Examples 5-2 to 5-4.

FIG. 51 is a diagram illustrating the results of reflection-spectrummeasurement of zinc oxide particles for light rays at wavelengths of 200nm to 2500 nm, the oxide particles being obtained in each of Example 5and Examples 5-2 to 5-4 of the present invention.

FIG. 52 is a graphic diagram illustrating the transmission spectrum forlight rays at wave lengths of 200 nm to 780 nm for a dispersion in whichzinc oxide particles are dispersed in propylene glycol obtained in eachof Example 5 and Examples 5-2 to 5-4.

FIG. 53 is a TEM photograph of zinc oxide particles obtained in Example5-6 of the present invention.

FIG. 54 is a diagram illustrating the results of IR measurement of zincoxide particles obtained in Example 5 and Example 5-6 of the presentinvention in a region at wavenumbers of 50 cm⁻¹ to 4000 cm⁻¹.

FIG. 55 is a graphic diagram illustrating the molar absorptioncoefficient for light rays at measurement wave lengths of 200 nm to 780nm for a dispersion in which zinc oxide particles are dispersed inpropylene glycol obtained in each of Example 5, Examples 5-5 to 5-7, andComparative Example 2-1.

FIG. 56 is a diagram illustrating the results of reflection-spectrummeasurement of zinc oxide particles for light rays at wavelengths of 200nm to 2500 nm, the oxide particles being obtained in each of Example 5and Examples 5-5 to 5-7 of the present invention.

FIG. 57 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm for the ratio of M-OHbonds contained in zinc oxide particles obtained in Example 5 andExamples 5-5 to 5-7 of the present invention.

FIG. 58 is a diagram illustrating a reflection spectrum of zinc oxideparticles for light rays at wavelengths of 200 nm to 780 nm, the oxideparticles being obtained in each of Example 5 and Examples 5-5 to 5-7 ofthe present invention.

FIG. 59 is a TEM photograph of zinc oxide particles obtained inComparative Example 2-1 of the present invention.

FIG. 60 is a TEM photograph of zinc oxide particles obtained inComparative Example 3-1 of the present invention.

FIG. 61 is a TEM photograph of zinc oxide particles obtained inComparative Example 3-2 of the present invention.

FIG. 62 is a diagram illustrating the results of STEM mapping ofcobalt-zinc-complex oxide particles obtained in Example 9 of the presentinvention.

FIG. 63 is a diagram illustrating, the results of a line analysis ofcobalt-zinc-complex oxide particles obtained in Example 9 of the presentinvention.

FIG. 64 is a diagram illustrating the results of STEM mapping ofcobalt-zinc-complex oxide particles obtained in Example 11 of thepresent invention.

FIG. 65 is a diagram illustrating the results of a line analysis ofcobalt-zinc-complex oxide particles obtained in Example 11 of thepresent invention.

FIG. 66 is a graphic diagram illustrating the transmission spectrum fora dispersion in which zinc oxide particles are dispersed in propyleneglycol obtained in each of Examples 9, 10, and 11.

FIG. 67 is a diagram illustrating a reflection spectrum ofcobalt-zinc-complex oxide particles obtained in Examples 9 to 11 of thepresent invention.

FIG. 68 is a diagram illustrating the results of STEM mapping ofsilicon-cobalt-zinc-complex oxide particles obtained in Example 13 ofthe present invention.

FIG. 69 is a diagram illustrating the results of a line analysis ofsilicon-cobalt-zinc-complex oxide particles obtained in Example 13 ofthe present invention.

FIG. 70 is a diagram illustrating reflection spectra ofcobalt-zinc-complex oxide particles obtained in Examples 9 to 11 andsilicon-cobalt-zinc-complex oxide particles obtained in Examples 12 to14 of the present invention.

DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described by way of exemplaryembodiments with reference to the attached drawings. However, theaspects of the present invention are not limited to the embodimentdescribed below. Oxide Particles)

The oxide particles according to the present invention are those inwhich the color characteristics, such as reflectance, transmittance,molar absorption coefficient, hue, or color saturation, are controlledby controlling the ratio of M-OH bonds contained in oxide particles. Theuse of oxide particles according to the present invention for acomposition intended to be applied to a coating film, a coated body, theskin of a human, or the like, or a film-like composition intended to beused for glass or the like enables effective coloring, while preventinga decrease in design, appearance, and texture. Thus, a coating orfilm-like oxide composition that can be effectively used for an objectto be coated can be provided.

(Configuration of Oxide Particles—1)

The oxide particles according to the present invention are thosecontaining one or more different elements other than oxygen or hydrogenobtained by way of reaction, crystallization, precipitation,co-precipitation, or the like. For the one or more different elementsother than oxygen or hydrogen, metal elements, or metalloid elements inthe chemical periodic table are preferable. Preferably, the metalloidelements used in the present invention may include, but not specificallylimited to, Si, Ge, As, Sb, Te, Se or the like. The oxide particles mayconsist of a single element of these metal and metalloid elements. Theoxide particles may be combined oxide particles consisting of aplurality of elements or may be combined oxide particles containingmetal and metalloid elements. In the case of oxide particles containingdifferent elements, the oxide particles may be in the form of the abovecombined oxide particles. Alternatively, as described later, the presentinvention can be embodied such that at least a part of the surface ofoxide particles may be coated with oxide containing elements differentfrom elements other than oxygen contained in the oxide particles.

(Configuration of Oxide Particles—2)

The oxide particles according to the present invention are not limitedto those composed of only oxides. The present invention can be embodiedby including a compound other than oxides to the extent that it does notaffect the present invention. Alternatively, the present invention canbe embodied such that oxide particles may be those containing a compoundother than oxides or combined oxide particles or oxide particles inwhich at least a part of the surface thereof is coated with a compoundother than oxides. Examples of the compound other than oxides includehydroxides, nitrides, carbides, various salts, such as nitrates andsulfates, hydrates, and organic solvates.

(Configuration of Oxide Particles—3)

As an example of the oxide particles according to the present invention,oxide particles in which at least a part of the surface thereof obtainedin Example 1-5 is coated with silicon oxide, which is one of siliconcompounds. FIG. 1 represents STEM mapping results of the siliconoxide-coated iron oxide particles obtained in Example 1-5. In FIG. 1,(a) is a dark field image (HAADF image), (b) is the mapping result ofsilicon (Si), (c) is the mapping result of iron (Fe), and (d) is themapping result of oxygen (O). As illustrated in FIG. 1, iron and oxygenare detected in the entire particles, and silicon is mainly detected onthe surface of the particles. FIG. 2 represents the results of a lineanalysis at the position indicated by the broken line in the HAADF imageof FIG. 1, the results showing the atomic % (mol %) of the elementdetected in the line segment from the end to the end of a particle. Asis evident from FIG. 2, oxygen and silicon were detected over the entireanalytical range in the line analysis. For iron, the inner side from theedge to several nm of the particle was detected. It is indicative of thefact that the surface of iron oxide is coated with silicon oxide. FIG. 3represents the results of STEM mapping of silicon oxide-coated oxideparticles obtained in Example 1 described later. FIG. 4 represents theresults of the line analysis at the position indicated by the brokenline in the HAADF image of FIG. 3. As is evident from FIGS. 3 and 4, theparticles obtained in Example 1 are different from those obtained inExample 1-5, the oxide particles are not entirely coated with siliconoxide, but are partially coated with silicon oxide and provided assilicon oxide-coated particles. Thus, as an example of the presentinventive oxide can be embodied as silicon compound-coated oxideparticles such that at least a part of the surface of oxide particles iscoated with a silicon compound.

(Description of M-OH Bonds—1)

FIG. 5 represents the results of FT-IR measurement of the siliconcompound-coated oxide particles obtained in Example 1 and Example 1-5 bythe ATR method (hereinafter abbreviated as IR measurement). Here, IR isabbreviation of the infrared absorption spectroscopy. The IR measurementresults of the silicon compound-coated oxide particles obtained inExample 1-5 can be seen such that, as compared with the results of IRmeasurement on the silicon compound-coated oxide obtained in Example 1,broad peaks around 1650 cm⁻¹ and around 3400 cm⁻¹ are small and broadpeaks in the vicinity of 800 cm⁻¹ to 1250 cm⁻¹ are shifted toward thehigher wavenumbers. In the present invention, among these peaks, thepeak in the vicinity of 3400 cm⁻¹ may be a peak derived from a hydroxylgroup (—OH), such as one in water, the peaks in the vicinity of 800 cm⁻¹to 1250 cm⁻¹ may be peaks that include peaks derived from the M-OHbonds. In the present invention, various color characteristics arecontrolled by controlling the M-OH bonds contained in oxide particles,and, for instance, the ratio of M-OH bonds can be determined from theIR-measurement results. The ratio of M-OH bonds may be measured by amethod other than IR measurement. Examples of such a method includeX-ray photoelectron spectroscopy (XPS), solid state nuclear magneticresonance (solid NMR), and electron energy loss spectroscopy (EELS).

(Description of M-OH Bonds—2)

The results of waveform separation of the peaks at wavenumbers of 100cm⁻¹ to 1250 cm⁻¹ in the IR measurement results are shown in FIG. 6 forExample 1 and in FIG. 7 for Example 1-5. In the above description, thevertical axis of the graph for IR measurement results represents thevalues of transmittance (% T), while the vertical axis for the waveformseparation represents the values of absorbance. In FIGS. 6 and 7,therefore, the vertical axis represents the values of absorbance. In thepresent invention, as a result of waveform separation of peaks atwavenumbers of 100 cm⁻¹ to 1250 cm⁻¹ in the IR measurement results, theoxide particles may be preferably oxide particles having controlledcolor characteristics. That is, the color characteristics are controlledsuch that the peaks waveform-separated at wavenumbers of 800 cm⁻¹ to1250 cm⁻¹ are provided as peaks derived from M-OH bonds, the peakswaveform-separated at wavenumbers of 100 cm⁻¹ to 800 cm⁻¹ are providedas peaks derived from M-O bonds, and the area ratio of the peakwaveform-separated for the M-OH bonds to the total area of each peak ofthe waveform-separated peaks is controlled in a region at wavenumbers of100 cm⁻¹ to 1250 cm⁻¹. In other words, in the results of the IRmeasurement in Example 1 shown in FIG. 6, the ratio of M-OH bondscontained in oxide particles is derived such that four peakswaveform-separated at wavenumbers of 100 cm⁻¹ to 800 cm⁻¹ are providedas peaks derived from M-O bonds, two peaks waveform-separated atwavenumbers of 800 cm⁻¹ to 1250 cm⁻¹ are provided as peaks derived fromM-OH bonds, and the area ratio of the peak waveform-separated for theM-OH bonds to the total area of each peak of the waveform-separatedpeaks is controlled in a region at wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹is calculated. As is evident from FIGS. 6 and 7, the total area ratio ofeach peak of the waveform-separated peaks for the M-OH bonds to thetotal peak components of waveform-separated peaks is found to be smallas compared with Example 1. In other words, it represents that the ratioof M-OH bonds contained in the oxide particles of Example 1-5 is lowerthan the ratio of M-OH bonds contained in the oxide particles ofExample 1. In the present invention, as an example of calculating theratio of M-OH bonds, waveform separation is performed on peaks atwavenumbers of 100 cm⁻¹ to 1250 cm⁻¹ in the IR measurement results, andthe area ratio (M-OH ratio [%]) calculated from the total area of M-OHbonds waveform-separated at waveforms of 800 cm⁻¹ to 1250 cm⁻¹ to thetotal area of all waveform-separated peaks is represented as the ratioof M-OH bonds.

(Description of M-OH Bonds—3)

Here, the oxide particles of Example 1 and Example 1-5 are siliconcompound-coated iron oxide particles prepared by coating the surface ofiron oxide particles with silicon oxide as described above. Thus, M inthe M-OH bonds is iron (Fe) or silicon (Si), and the M-OH bonds can beidentified as Fe—OH bonds or Si—OH bonds. Also, the M-O bond can bespecified as a Fe—O bond or a Si—O bond just as in the case with theM-OH bond. The present invention has found that the colorcharacteristics of the oxide particles can be controlled such that peaksat wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹ are waveform-separated, and thepeaks waveform-separated at wavenumbers of 800 cm⁻¹ to 1250 cm⁻¹ arerecognized as peaks derived from the M-OH bonds, and then the area ratio(M-OH ratio [%]) calculated from the total area of the M-OH bonds withrespect to the total area of all the waveform-separated peaks iscontrolled. In the present invention, however, among peakswaveform-separated at wavenumbers of 800 cm⁻¹ to 1250 cm⁻¹, peaks whichcan be attributed to those different from the M-OH bonds, are notlimited to belonging to the M-OH bonds. For instance, among peakswaveform-separated at wavenumbers of 800 cm⁻¹ to 1250 cm⁻¹ which wasidentified as M-OH bonds in Example 1, peaks waveform-separated in thevicinity of 1044 cm⁻¹ and peaks waveform-separated in the vicinity of1061 cm⁻¹ and 1188 cm⁻¹ in Example 1-5 can be identified as M-O bonds(Si—O bonds) for the silica skeleton structure, but not be identified asM-OH bonds (Si—OH bonds) (e.g., the peaks can be attributed in thevicinity of 1044 cm⁻¹: stretching vibration of ≡Si—O—Si═, in thevicinity of 1061 cm⁻¹: Si—O stretching vibration of the silica skeleton,in the vicinity of 1188 cm⁻¹:stretching vibration of ≡Si—O—Si≡, so thatthey can be recognized as M-O bonds (Si—O bonds). In this way, byfurther subdividing peaks waveform-separated at wavenumbers of 800 cm⁻¹to 1250 cm⁻¹ into the M-OH bonds and other bonds different from M-OHbonds, such as M-O bonds to derive the ratio of M-OH bonds, the ratio ofM-OH bonds may be controlled in more detail to control the colorcharacteristics of the oxide particles. Alternatively, the ratio of M-OHbonds may be controlled to control the color characteristics of theoxide particles by deriving the ratio of M-OH bonds bywaveform-separating only the peaks at wavenumbers of 800 cm⁻¹ to 1250cm⁻¹.

(Description of M-OH Bonds—4)

FIG. 8 represents XRD measurement results of the oxide particlesobtained in Example 1-5. As is evident from FIG. 8, no peak is observedother than the peaks derived from α-Fe₂O₃. Also in Example 1, no peak isobserved other than the peaks derived from α-Fe₂O₃ (not shown).Nevertheless, in the IR measurement results, peaks derived from the M-OHbonds were detected. Thus, the M-OH bonds are mainly present on thesurface of oxide particles rather than the inside thereof. In the XRDmeasurement results, therefore, it is thought that no peak of hydroxideor the like were not detected. Further, the XRD measurement resultsshowed that the silicon compound confirmed by the above IR measurementcontains amorphous.

(Specific Examples of Ratio of M-OH Bonds and Color Characteristics)

FIG. 9 represents reflection spectra of oxide particles respectivelyobtained in Example 1 and Examples 1-2 to 1-5 for light rays atwavelengths of 200 nm to 2500 nm. First, as is evident from the figure,with respect to the reflectance for the light rays of the near-infraredregion at wavelengths of 780 nm to 2500 nm, the silicon compound-coatedoxide particles obtained in Example 1-5 is higher than the siliconcompound-coated oxide particles obtained in Example 1. Waveformseparation was performed on peaks at wavenumbers of 100 cm⁻¹ to 1250cm⁻¹ in the IR spectrum. For the area ratio of the peaks of M-OH bondsto the total area of each waveform-separated peak (M-OH ratio [%]),descending order is Example 1-5, Example 1-4, Example 1-3, Example 1-2,and Example 1. For the average reflectance for light rays at wavelengthsof 780 nm to 2500 nm, ascending order is Example 1-5, Example 1-4,Example 1-3, Example 1-2, and Example 1. The average reflectance forlight rays at wavelengths of 780 nm to 2500 nm refers to the simpleaverage value of the reflectance values at all the respectivemeasurement wavelengths in a wavelength region of 780 nm to 2500 nm.FIG. 10 represents a graph of the average reflectance for light rays atwavelengths of 780 nm to 2500 nm for the ratio of M-OH [%]. As isevident from FIG. 10, the lower the ratio of M-OH, the higher theaverage reflectance for light rays at wavelengths of 780 nm to 2500 nmtended to be observed. In other words, the oxide particles of thepresent invention are the oxide particles having as one of the colorcharacteristics the average reflectance for light rays at wavelengths of780 nm to 2500 nm controlled by controlling the ratio of M-OH bondscontained in the oxide particles, and preferably having the averagereflectance for light rays at wavelengths of 780 nm to 2500 nm enhancedby lowering the ratio of M-OH bonds. Furthermore, when the oxideparticles are silicon compound-coated oxide particles, the M-OH bondscan be Fe—OH bonds or Si—OH bonds. Thus, by controlling the ratio ofM-OH bonds to 8% or more and 14.5% or less, the average reflectance ofthe oxide particles for light rays at wavelengths of 780 nm to 2500 nmcan be 50% or more in the resulting silicon compound-coated oxideparticles.

(Control of Ratio of M-OH Bonds and Color Characteristics)

In the present invention, in a manner similar to the reflectance oraverage reflectance for light rays in a near-infrared region, or at thewavelengths of 780 nm to 2500 nm, the ratio of M-OH bonds contained inoxide particles is controlled to allow the oxide particles to havecorrectly and properly controlled color characteristics. Here, the colorcharacteristics include, for example, molar absorption coefficient,average molar absorption coefficient, or transmittance for light rays ina ultraviolet region, or at wavelengths of 190 nm (200 nm) to 380 nm;and reflectance, average reflectance, transmittance, or averagetransmittance for light rays in a visible region, or at wavelengths of380 nm to 780 nm; and hue H (=b*/a*) or color saturationC(=((a*)²+(b*)²)^(1/2)) in an L*a*b* colorimetric system. In particular,therefore, oxide particles suitable for use in a coating or film-likecomposition can be provided.

(Color Characteristics: Average Molar Absorption Coefficient)

From the absorbance and the molar concentration of a substance to bemeasured in a measurement sample in an ultraviolet-visible absorptionspectrum measurement, a molar absorption coefficient can be calculatedby the following equation 1:ε=A/(c·l)  (Equation 1)wherein ε is a constant inherent to the substance and referred to as amolar absorption coefficient, and corresponds to the absorbance of a 1mol/L dispersion medium with a thickness of 1 cm, and thus the unit isL/(mol·cm). In the equation, “A” is an absorbance in ultraviolet-visibleabsorption spectrum measurement; “c” is the molar concentration (mol/L)of a sample; and “l” is the length through which light is transmitted(optical path length) (cm), and is usually the thickness of a cell usedin the measurement of ultraviolet-visible absorption spectrum. In thepresent invention, to demonstrate the ability to absorb light rays inthe ultraviolet region of wavelengths of 190 nm (200 nm) to 380 nm, inthe measurement wavelength region of wavelengths of 190 nm (200 nm) to380 nm, a simple average of molar absorption coefficients at all themeasurement wavelengths is calculated and evaluated as an average molarabsorption coefficient.

(Color Characteristics: Average Reflectance Value or AverageTransmittance)

As described above, furthermore, the average reflectance for light raysat wavelengths of 780 nm to 2500 nm refers to the simple average valueof the reflectance values at all the respective measurement wavelengthsfor a reflection spectrum in a wavelength region of 780 nm to 2500 nm.Furthermore, the average transmittance at wavelengths of 380 nm to 780nm refers to the simple average value of the transmittances at all therespective measurement wavelengths for a transmittance spectrum in aregion at wavelengths of 380 nm to 780 nm.

The average molar absorption coefficient, average reflectance, andaverage transmittance are not limited to the above-described wavelengthranges, and a wavelength region to be averaged according to the intendedcolor characteristics can be set appropriately.

(Color Characteristics: Hue or Color Saturation)

Hue and color saturation in the present invention can be represented byhue H (=b*/a*, b*>0, a*>0) in an L*a*b* colorimetric system and colorsaturation C=((a*)²+(b*)²)^(1/2). Here, the L*a*b* colorimetric systemis one of the uniform color space, and L* is a value representing thebrightness, and the larger the numerical value, the brighter it is.Also, a* and b* represent chromaticity. In the present invention, thecolorimetric system is not limited to the L*a*b* colorimetric system.The color characteristics may be evaluated using any of othercolorimetric systems, such as an XYZ system.

(Control of Ratio of M-OH Bonds: Description of Method—1)

In the present invention, the method for controlling the ratio of M-OHbonds is not particularly limited, but it is preferable to control theratio of M-OH bonds by modification of functional groups contained inoxide particles. The functional modification can control the ratio ofM-OH bonds by a method for subjecting the functional groups contained inoxide particles to a process using a substitution reaction, additionreaction, elimination reaction, dehydration reaction, condensationreaction, or the like. For controlling the ratio of M-OH bonds, theratio of M-OH bonds may be increased or decreased. In the presentinvention, preferably, the above control may esterify the M-OH bonds.The esterification is accomplished, for example, by adehydration/condensation reaction in which OH is detached from acarboxyl group (—COOH) and H is detached from a hydroxyl group (—OH).The ratio of M-OH bonds can also be controlled by a method for allowinghydrogen peroxide or ozone to act on oxide particles. For precipitatingoxide particles in a liquid, the ratio of M-OH bonds may be controlledby a formulation for precipitating the oxide particles, a method forcontrolling pH, or the like. As an example of the dehydration reaction,the ratio of M-OH bonds may be controlled by a method for heat-treatingthe oxide particles. For controlling the ratio of M-OH bonds by themethod for heat-treating oxide particles, a dry-heat treatment may beperformed. Alternatively, the oxide particles may be dispersed in adispersion medium and the resulting dispersion may be then subjected toa heat treatment. As will be described later, the ratio of M-OH bondsmay be controlled by dispersing oxide particles in a target solvent,adding a substance containing functional groups to the dispersionliquid, and subjecting the dispersion to a treatment, such as stirring.The ratio of M-OH bonds may be controlled by subjecting them to atreatment, such as stirring, in a dispersion liquid containingprecipitated oxide particles. Furthermore, the ratio of M-OH bonds maybe controlled using an apparatus in which a dispersing device and amembrane filter are communicated with each other. That is, when a methodfor removing impurities from a slurry containing oxide particles bytreating the particles with a dispersion treatment and cross-flowmembrane filtration, the temperature of the slurry, the temperature of awashing liquid used for cross-flow, or the like is changed to controlthe ratio of M-OH bonds. In this case, a uniform modification can beperformed on the primary particles of oxide particles, particularly thesurfaces of the respective primary particles. There is therefore anadvantage that the ratio of M-OH bonds contained in oxide particles andthe color characteristics thereof can be controlled more closely andhomogeneously.

For the adjustment of pH for precipitation of the oxide particles, a pHmodulator, such as an acidic or basic substance, may be included in atleast one of various solution and solvents in the present invention.Alternatively, the pH may be adjusted by changing the flow rate whenmixing a fluid containing an oxide raw material with an oxideprecipitation solvent.

The method for changing a functional group contained in the oxideparticles according to the present invention is not particularlylimited. The functional group may be changed by dispersing the oxideparticles in a target solvent, adding a substance containing afunctional group to the dispersion, and subjecting the dispersion to atreatment such as stirring. Alternatively, it may be carried out bymixing a fluid containing the oxide particles with a fluid containing asubstance having functional groups using the above micro-reactor.

The substance containing a functional group is not particularly limited,but is a substance containing a functional group that can be substitutedwith a hydroxyl group contained in the oxide particles. Examples of sucha substance include: acylating agents, such as acetic anhydride andpropionic anhydride; methylating agents, such as dimethyl sulfate anddimethyl carbonate; and silane coupling agents, such aschlorotrimethylsilane and methyl trimethoxysilane.

As described above, the ratio of M-OH bonds can be controlled by amethod for allowing hydrogen peroxide or ozone to act on oxideparticles. The method for allowing hydrogen peroxide or ozone to act onoxide particles is not particularly limited. It may be performed bydispersing oxide particles in a target solvent and adding a solution,such as hydrogen peroxide or ozone, or an aqueous solution containingthem to the dispersion, followed by treatment, such as stirring.Alternatively, it may be performed by mixing a fluid containing oxideparticles and a fluid containing hydrogen peroxide or ozone using themicro-reactor described above.

The dispersion may be a liquid dispersion in which oxide particles aredispersed in a liquid dispersion medium, such as water, an organicsolvent, or resin, or may be a film-like dispersion prepared by using adispersion liquid containing oxide particles. When heat treatment isperformed in a state of a dispersion containing oxide particles,agglomeration of particles can be suppressed as compared with a heattreatment in a dry state. For example, when the oxide particles of thepresent invention are used for a multilayer-coating film and ahigh-design multilayer-coating film as described in JP 2014-042891 andJP 2014-042892, the color characteristics of the oxide particles can becontrolled by controlling the ratio of M-OH bonds contained in the oxideparticles by heat treatment or the like after the oxide particles areformed into the multilayer coating film or the multilayer coating film.Thus, such a use is therefore suitable for reduction of the number ofsteps and strict control of color characteristics. Incidentally, themultilayer coating film and the highly designed multilayer coating filmdescribed in JP 2014-042891 and JP 2014-042892 have a high differencebetween highlight and shade for a specific color, the intensity largelyvaries depending on the observation angle, thereby realizing the senseof depth and denseness. It is therefore required to improve thetransmittance for a specific color in order to enhance highlight and toincrease the difference between highlight and shade. Such a coating filmprovided as an oxide particle dispersion can increase its transparency,which serves as the ability to absorb ultraviolet rays of oxideparticles, as its molar absorption coefficient in the ultravioletregion, which is the ability to absorb ultraviolet rays of oxideparticles, is larger. In addition, a reduction in the amount of oxideparticles used can also reduce the haze value.

The oxide particles, such as silicon compound-coated zinc oxideparticles, can be applied to applications other than the above-mentionedapplication for laminated coating films. For example, the oxideparticles can be dispersed in a laminated glass, which sandwiches anintermediate film of resin or the like between plate glasses and isadhered thereto, a film-like composition used for glass of a building,or the like to suitably improve the absorption of ultraviolet rays andthe reflection of near infrared rays. Further, since the oxide particlescan enhance the transmission properties to visible light, the oxideparticles can be also suitably used as an oxide composition for UVprotection and near-infrared protection-purpose glass. The colorcharacteristics of oxide particles can be controlled by controlling theratio of M-OH bonds contained in the oxide particles. That is, afterdispersing the oxide particles into glass, resin, or the like in amanner similar to the above laminated coating film, the functionalgroups in the oxide particles are changed by heat treatment or the liketo control the color characteristics. This procedure is suitable forreduction of the number of steps as well as control of strict colorcharacteristics like the above-mentioned multilayer coating film.

(Preferred Embodiment of Oxide Particles—1)

In the present invention, the primary particle diameter of the oxideparticles is preferably in the range of 1 nm or more and 100 nm or less,and more preferably 1 nm or more and 50 nm or less. As described above,the ratio of M-OH bonds contained in the oxide particles may existmainly on the surface of the particles. Thus, the oxide particles havinga primary particle diameter of 100 nm or less have an increased surfacearea as compared with oxide particles having a primary particle diameterof more than 100 nm. Controlling the ratio of M-OH bonds of the oxideparticles may have a large influence on color characteristics, such asabsorption, reflection, hue, or color saturation. Thus, the oxideparticles having a primary particle diameter of 100 nm or less have anadvantage that the predetermined color characteristics, particularlythose suitable for use as a coated product or film, can be suitablyexhibited by controlling the ratio of M-OH bonds contained in the oxideparticles.

(Preferred Embodiment of Oxide Particles—2)

In the present invention, preferably, for the oxide particles coatedwith at least a part of the surface of the particles, such as thesilicon compound-coated iron oxide particles, the ratio of the averageprimary particle diameter of the oxide particles after coating with thecompound to the average primary particle diameter of the oxide particlesbefore coating is 100.5% or more and 190% or less. If the coating of thecompound on the oxide particles is too thin, there is a possibility thatthe effect on the color characteristics of the oxide particles coatedwith the compound cannot be exhibited. Preferably, therefore, theaverage primary particle diameter of the oxide particles after coatingwith the compound may be 100.5% or more of the average primary particlediameter of the oxide particles. In addition, in the case where thecoating is too thick or when covered with coarse aggregates, it isdifficult to control the color characteristics. Preferably, therefore,the average primary particle diameter of the oxide particles aftercoating with the compound may be 190% or less of the average primaryparticle diameter of the oxide particles. The oxide particles coatedwith the compound according to the present invention may be a core-shelltype compound-coated oxide particles in which the entire surface of theoxide particles serving as a core are uniformly coated with thecompound. Furthermore, the compound-coated oxide particles arepreferably compound-coated oxide particles in which two or more oxideparticles are not aggregated and at least a part of the surface of asingle oxide particle is coated with a compound. It may becompound-coated oxide particles in which at least a part of the surfaceof an aggregate formed by aggregation of a plurality of oxide particleswith is coated with a compound.

(Preferred Embodiment of Oxide Particles—3)

The compound that covers at least a part of the surface of the oxide inthe present invention is preferably a silicon compound, more preferablya compound containing silicon oxide, and still more preferably acompound containing amorphous silicon oxide. By including the amorphoussilicon oxide in the silicon compound, it is possible to strictlycontrol the color characteristics, such as transmittance, molarabsorption coefficient, hue, and saturation, of the siliconcompound-coated oxide particles. In the case where the silicon compoundis crystalline silicon oxide, it is extremely difficult to cause M-OH(Si—OH) to exist, so that it may be difficult to control the colorcharacteristics of the present invention in some cases.

(Method for Producing Oxide Particles: Apparatus)

Examples of the method for producing oxide particles according to thepresent invention include a process in which oxide particles areprepared by using a dilution-type reaction in a micro-reactor, a batchvessel, or by a pulverization method using a bead mill or the like; and,simultaneously with or after the preparation, controlling the ratio ofM-OH bonds contained in oxide particles in a reaction vessel or thelike. Furthermore, the apparatus and the method as described in JP2009-112892, which are proposed by the applicant of the presentapplication, may be used to control the production of oxide particles orto control both the production of oxide particles and the ratio of M-OHbonds contained in the oxide particles. The apparatus described in JP2009-112892 has a stirring tank having an inner circumferential surfacehaving a circular cross section and an agitating tool attached to theinner circumferential surface of the stirring tank with a slight gaptherebetween. The stirring vessel comprises at least two fluid inletsand at least one fluid outlet. One of the fluid inlets introduces afirst processed fluid containing one of the reactants among fluids to beprocessed into the stirred vessel. From the other one of the fluidinlets, a second processed fluid containing one of reactants differentfrom the above reactant is introduced into the stirring vessel from aflow path different from the first treated fluid. At least one of thestirring tank and the stirring device rotates at a high speed withrespect to the other, thereby bringing the fluid to be processed into athin film state. In this thin film, the reactants included in at leastboth the first and second fluids to be treated are brought into reactwith each other. In order to introduce three or more fluids to betreated into the stirring tank, as illustrated in FIGS. 4 and 5 of thepublication, three or more introduction pipes may be provided. Examplesof the micro-reactor include apparatuses having the same principle asthe fluid treatment apparatuses described in Patent Literatures 5 and 6.

As an example of the method for producing oxide particles according tothe present invention, it is preferred to use a method for producingoxide particles by preparing a oxide raw-material liquid containing atleast raw materials of oxide particles and a oxide-precipitation solventcontaining at least an oxide precipitation substance for precipitatingoxide particles, and producing oxide particles in a mixture fluid inwhich the oxide raw-material liquid and the oxide-precipitation solventusing a method of reaction, crystallization, separation,co-precipitation, or the like. As described above, in the method forproducing oxide particles by the method of reaction, crystallization,separation, co-precipitation, or the like of the oxide particles, theparticles having the ratio of M-OH bonds controlled to a predeterminedvalue may be produced.

For the raw materials of the oxide particles in the present invention,it is not limited in particular. Any raw material that can be formedinto an oxide by the method of reaction, crystallization, separation,co-precipitation, or the like may be applicable. For example, metal ormetalloid elementary substances and compounds can be exemplified.Furthermore, in the present invention, the above metal or metalloidcompounds are collectively referred to as a compound. Examples of thecompound include, but not limited to, metal or metalloid salts, oxides,hydroxides, hydroxide oxides, nitrides, carbides, complexes, organicsalts, organic complexes, organic compounds, and hydrates and organicsolvates thereof. Examples of metal or metalloid salts include, but notparticularly limited to, metal or metalloid nitrates and nitrites,sulfates and sulfites, formates and acetates, phosphates, phosphites,hypophosphites and chlorides, oxy salts or acetylacetonate salts orhydrates thereof, organic solvates, and the like. Examples of theorganic compound include metal or metalloid alkoxides and the like.These metals or metalloid compounds may be used alone or may be used incombination of two or more.

Further, as in the case that the oxide particles are siliconcompound-coated oxide particles, examples of silicon compound rawmaterials in the case of oxide particles containing a silicon compoundinclude oxides and hydroxides of silicon, as well as compounds ofsilicon salts, alkoxides, and the like, and hydrates thereof. Examplesof the compound include, but not limited to, silicates, such as sodiumsilicate, phenyltrimethoxysilane, methyltrimethoxysilane,methyltriethoxysilane, 3-glycidoxypropyl trimethoxysilane,3-trifluoropropyl-trimethoxysilane, methacryloxypropyl triethoxysilane,tetramethoxysilane (TMOS), tetra Ethoxysilane (TEOS), oligomercondensates of TEOS, such as ethyl silicate 40, tetraisopropylsilane,tetrapropoxysilane, tetraisobutoxysilane, and tetrabutoxysilane, andother substances similar to any of them. As raw materials of the siliconcompounds, furthermore, bis(triethoxysyril) methane, 1,9-bis(triethoxycyril) nonane, diethoxy dichlorosilane, triethoxychlorosilane, or the like may be used. When the oxide particles in thepresent invention are silicon compound-coated oxide particles, siliconmay be preferably contained in an amount of 2 to 80%, more preferably 5to 50% in relation to an element other than oxygen that constitutesoxide particles to be coated. The amount and type of the siliconcompound material can be appropriately selected on the basis of the typeof target oxide particles.

When the raw materials of the oxide particle or the silicon compound aresolid, the raw materials of oxide particles may be in a molten state ora state in which the raw materials of the oxide particles are mixed ordissolved in a solvent (including a state of molecular dispersion). Evenwhen the raw materials of the oxide particles are liquid or gas, the rawmaterials may be preferably used in a state of being mixed or dissolvedin a solvent described later (including a state of moleculardispersion).

The oxide precipitation substance is not particularly limited as long asit is a substance capable of precipitating the raw materials of oxideparticles contained in an oxide raw-material liquid as oxide particles.For example, an acidic substance or a basic substance can be used. Atleast an oxide-precipitation substance is preferably used in a statebeing mixed, dissolved, and molecularly dispersed in a solvent describedlater.

Examples of the basic substance include metal hydroxides, such as sodiumhydroxide and potassium hydroxide; metal alkoxide, such as sodiummethoxide and sodium isopropoxide; amine compounds, such astriethylamine, diethylaminoethanol, and diethylamine; and ammonia.

Examples of the acid substance include inorganic acids, such as aquaregia, hydrochloric acid, nitric acid, fuming nitric acid, sulfuricacid, and fuming sulfuric acid; and organic acids, such as formic acid,acetic acid, chloroacetic acid, dichloroacetic acid, oxalic acid,trifluoroacetic acid, trichloroacetic acid, and citric acid. The basicsubstance and the acidic substance can also be used for precipitatingoxide particles. In addition, as described above, these substances canalso be used as pH-adjusting agents for controlling the ratio of M-OHbonds contained in the oxide particles.

(Solvent)

Examples of the solvent used as a solvent for any of the oxideraw-material liquid and the oxide precipitation solvent include, forexample, water, an organic solvent, and a mixed solvent composed of twoor more of them. Examples of the water include tap water, ion-exchangedwater, pure water, ultrapure water, and RO water (reverse osmosiswater). Examples of the organic solvent include an alcohol compoundsolvent, an amide compound solvent, a ketone compound solvent, an ethercompound solvent, an aromatic compound solvent, an carbon disulfide, analiphatic compound solvent, a nitrile compound solvent, a sulfoxidecompound solvent, a halogen compound solvent, an ester compound solvent,an ionic liquid, a carboxylic acid compound, and a sulfonic acidcompound. The above solvents may be used alone or may be used as amixture of two or more. Examples of the alcohol compound solvent includemonohydric alcohols, such as methanol and ethanol, and polyols, such asethylene glycol and propylene glycol.

(Dispersants, Etc.)

In the present invention, various additives, such as various dispersantsand surfactants, may be used on the basis of purpose and necessity asfar as they do not adversely affect the preparation of oxide particles.As a dispersant or surfactant, but not particularly limited to, any ofvarious generally used and commercially available products, manufacturedgoods, and newly synthesized products can be used. For example, anionicsurfactants, cationic surfactants, nonionic surfactants, and dispersingagents, such as various polymers, can be included. These dispersants andsurfactants may be used alone or in combination of two or more of them.The surfactant and dispersant described above may be contained in atleast one of the oxide raw material liquid and the oxide precipitationsolvent. Further, the surfactant and the dispersant described above maybe contained in another fluid different from the oxide raw materialliquid and the oxide precipitation solvent.

(Control of Ratio of M-OH Bonds: Outline of Method)

In the present invention, the ratio of M-OH bonds is controlled. Here,the M-OH bond is a bond between a hydroxyl group (OH) and a single ortwo or more different elements (M) other than oxygen or hydrogencontained in the oxide particles as described above. As a concretemethod, the control can be performed in two steps: one for preparinguntreated oxide particles having a predetermined primary particlediameter, which can be a target for the control of the ratio of M-OHbonds; and other for treating the untreated oxide particles to controlthe ratio of M-OH bonds contained in such oxide particles. However, inthe step of preparing the untreated oxide particles, the production ofoxide particles by precipitation or the like may be performed such thatparticles in which the ratio of M-OH bonds is controlled to apredetermined value.

(Coating Composition or Film-like Composition—1)

The coating oxide composition or film-like oxide composition of thepresent invention is applicable to any of those described in JP2014-042891 and JP 2014-042892, but not particularly limited thereto.Alternatively, for example, it is applicable to any of those for variouskinds of paints, such as solvent-based paints and water-based paints. Ifnecessary, the coating oxide composition may further contain additivesproperly based on the purpose. Examples of the additive may include, inaddition to pigments and dyes, a wetting agent, a dispersing agent, acolor separation-preventing agent, a leveling agent, a viscosityadjusting agent, an anti-skinning agent, an anti-gelling agent, ananti-foaming agent, a thickener, an anti-sagging agent, a fungicide, anultraviolet absorber, a film-forming aid, a surfactant, and a resincomponent. Examples of the resin component for the purpose of paintingmay include a polyester resin, a melamine resin, a phenol resin, anepoxy resin, a vinyl chloride resin, an acrylic resin, an urethaneresin, a silicone resin, and a fluorine resin. A coated product to whicha paint containing the coating oxide composition of the presentinvention is applied may be a single coated product composed of a singlelayer coated product, or a multilayer coated product composed of aplurality of coating compositions, such as those for laminated coatingfilms as described in JP 2014-02891 and JP 2014-042892. Alternatively,such a coated product may be included in a paint containing a pigment orany of other paints, such as a clear paint. When the film-likecomposition is intended, the composition may include as needed a binderresin, a curing agent, a curing catalyst, a leveling agent, asurfactant, a silane coupling agent, a coloring agent such as adefoaming agent, a pigment or a dye, an antioxidant, and the like.

(Coating Composition or Film-like Composition—2)

The coating oxide composition or the film-like oxide compositionaccording to the present invention comprises: oxide particle power; adispersion in which oxide particles are dispersed in a liquid dispersionmedium; and oxide particles in the form of a dispersion in which oxideparticles are dispersed in a solid, such as a glass or resin, or in aliquid or the like before solidification. The oxide particles containedin the coating oxide composition or in the film-like oxide compositionmay be composed of one oxide particle, or may be composed of anaggregate formed of a plurality of oxide particles being aggregated, ormay be a mixture of both compositions. If the aggregate is composed of aplurality of oxide particles being aggregated, the diameter of theaggregate is preferably 50 nm or less. Further, the oxide compositionmay be used as one being dispersed in cosmetics or paint together withvarious pigments, or may be over-coated on a coating film. Furthermore,oxide particles can be used as a sole pigment. Examples of the liquiddispersion medium include water, such as tap water, distilled water, ROwater (reverse osmic water), pure water, and ultrapure water; an alcoholsolvent, such as methanol, ethanol, and isopropyl alcohol; a polyhydricalcohol solvent, such as propylene glycol, ethylene glycol, diethyleneglycol, and glycerin; an ester solvent, such as ethyl acetate and butylacetate; an aromatic solvent, such as benzene, toluene, and xylene; aketone solvent, such as acetone and methyl ethyl ketone; a nitrilesolvent such as acetonitrile; a silicone oil; a vegetable oil; and awax. These dispersion media may be used alone or may be used incombination of two or more.

(Color of Coating Composition or Film-like Composition)

The color of the coated product, film, or glass is not particularlylimited. The coating oxide composition or film-like composition of thepresent invention can be used for the desired hue. The dye or pigmentmay be suitably formulated with a coating composition used in a coatedproduct of white family, gray family, black family, for example colorsfrom white color with the lightness of 10 to black color with thelightness of 0 in the Munsell colorimetric system; yellow to greenfamilies, for example colors with the hue of Y to BG in the Munsell huecircle; or blue to purple families, for example colors with the hue of Bto P in the Munsell hue circle (each including metallic color). However,the colors are not limited to these colors, and colors with other huesmay be applicable. Furthermore, a coating composition containing theoxide particles of the present invention can be suitably used for acoating film or a topcoat of a coated body exhibiting any of thesecolors to remarkably reduce loss of color development of each color. Thedesign of the coated body can be therefore improved. Various pigmentsand dyes can be used as necessary for the pigment or dye contained inthe coating composition. For example, all pigments and dyes registeredin the color indexes can be used. Among them, for example, pigments forgreen color are pigments and dyes classified as C.I. I. Pigment Green;pigments for blue color are pigments and dyes classified as C.I. I.Pigment Blue; pigments for white color are pigments and dyes classifiedas C.I. I. Pigment Blue; pigments for yellow color are pigments and dyesclassified as C.I. I. Pigment Yellow; pigments and dyes for red colorare pigments and dyes classified as C.I. I. Pigment Red; and pigmentsand dyes for violet color are pigments and dyes classified as C.I. I.Pigment Violet. More specifically, the pigments and dyes include, forexample, quinaridone pigments, such as C.I. I. Pigment Red 122 and C.I.I. Pigment Violet 19; diketopyrrolopyrrole pigments, such as C.I. I.Pigment Red 254 and C.I. I. Pigment Orange 73, such as such asquinaridone pigments; naphthol pigments, such as C. I. Pigment Red 150and C.I. 1. Pigment Red 170; perylene pigments, such as C. I. PigmentRed 123 and C.I. I. Pigment Red 179; and azo pigments, such as C. I. AzoPigment Red 144. These pigments and dyes may be used alone or may beused in combination of two or more. Here, the oxide composition of thepresent invention may be used alone without being mixed with any of theabove pigments and dyes or may be formulated in a coating or film-likecomposition. By containing the oxide particles in the coatingcomposition according to the present invention, it is possible toconstruct a coated product having higher color saturation and a largedifference between highlight and shade when used for laminated coating,for example, as described in JP 2014-04289 and JP 2014-042892. In otherwords, the coating composition containing the oxide particles ispreferable because white sharpness does not occur in the shade, sharpmetallic texture or the like can be obtained by an increase in blacknesslevel, and the like. The oxide particles can be preferably included in afilm-like composition for use in a transparent substrate, such as glassfor buildings, vehicles, displays, and the like, because of itsadvantages of: effectively absorbing and shielding ultraviolet ray toenhance the safety to the human body, thereby suppressing thedecomposition of organic matters or the like inside buildings andvehicles; effectively reflecting and shielding near infrared rays,thereby suppressing an increase in temperature in buildings andvehicles; and exhibiting high transmission properties to visible light.Thus, a film or glass with high transparency can be provided.

EXAMPLE

Hereinafter, the present invention will be described in more detail withreference to examples, but the present invention is not limited to onlythese examples. Pure water used in the examples below was of aconductivity of 0.86 μS/cm (measurement temperature: 25° C.), unlessotherwise noted.

(Preparation of Samples for TEM Observation and Preparation of Samplesfor STEM Observation)

A part of the wet cake sample of oxide particles obtained in Exampleswas dispersed in propylene glycol and further diluted 100 times withisopropyl alcohol (IPA). The obtained diluted liquid was dropped on acollodion membrane or micro grid and dried to prepare a sample for TMobservation or a sample for STEM observation.

(Transmission Electron Microscope and Energy Dispersive X-Ray AnalysisApparatus: TEM-EDS Analysis)

For observation and quantitative analysis of oxide particles by TEM-EDSanalysis, a transmission electron microscope JEM-2100 (manufactured byJEOL Ltd.) equipped with an energy dispersive X-ray analyzer JED-2300(manufactured by JEOL Ltd.) was used. For observation, conditions werean acceleration voltage of 80 kV and a magnification of ×25,000 or more.The particle diameter was calculated from the distance between themaximum outer circumferences of the oxide particles observed by TEM, andthen the average value (average primary particle diameter) of theresults of measuring the particle diameters of 100 particles werecalculated. The molar ratio of the elemental components constituting theoxide in the oxide particles was calculated by TEM-EDS, and then theaverage value of the results of calculating the molar ratio for 10 ormore particles was calculated.

(Scanning Transmission Electron Microscope and Energy Dispersive X-rayAnalysis Apparatus: STEM-EDS Analysis)

For the mapping and quantification of elements contained in the oxideparticles by STEM-EDS analysis, an atomic resolution analytical electronmicroscope JEM-ARM 200F (manufactured by JEOL Ltd.) equipped with anenergy dispersive X-ray analyzer Centurio (manufactured by JEOL Ltd.)was used. For observation, conditions were an acceleration voltage of 80kV, a magnification of ×50,000 or more, and a beam size of 0.2 nm indiameter.

(X-ray Diffraction Measurement)

For X-ray diffraction (XRD) measurement, a powder X-ray diffractometerEMPYREAN (manufactured by PANalytical Division, Spectris Co., Ltd.) wasused. Measurement conditions were as follows: a measurement range of 10to 100 [degrees 2-Theta], a Cu anticathode, a tube voltage of 45 kV, atube current of 40 mA, and a scan rate of 0.3 degrees per minute. XRDmeasurement was carried out on the dry powder of oxide particlesobtained in each example.

(FT-IR Measurement)

FT-IR measurement was carried out using a Fourier transform infraredspectrophotometer FT/IR-6600 (manufactured by JAJASCO Corporation). Themeasurement conditions were a resolution of 4.0 cm⁻¹ and an accumulatednumber of 1024, using an ATR method under nitrogen atmosphere. Waveformseparation of peaks at wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹ in theinfrared absorption spectrum was performed using the spectral analysisprogram attached to the control software of FT/IR-6600 mentioned aboveto give a residual square sum of 0.01 or less. Measurement was carriedout using dry powder of oxide particles obtained in Examples.

(Transmission Spectrum, Absorption Spectrum, Reflection Spectrum, Hue,and Color Saturation)

An ultraviolet-visible/near-infrared spectrophotometer (product name:V-770, manufactured by JAJASCO Corporation) was used for transmissionspectrum, absorption spectrum, reflection spectrum, hue, and colorsaturation. The transmission spectrum was measured at 190 nm to 800 nmor 200 nm to 800 nm and the absorption spectrum at 190 nm to 800 nm or200 nm to 800 nm, with a sampling rate of 0.2 nm at a low measurementrate. For a specific wavelength region, the values of transmittance at aplurality of measurement wavelengths were simply averaged and providedas the average transmittance. After measuring the absorption spectrum, amolar absorption coefficient at each measurement wavelength wascalculated from both the absorbance obtained from the measurement resultand the concentration of oxide in the dispersion. The results aregraphically represented; the measurement wavelength is plotted on thehorizontal axis and the molar absorption coefficient is plotted on thevertical axis. The measurement employed a liquid cell of 1 cm inthickness. Further, the molar absorption coefficients at a plurality ofmeasurement wavelengths of 190 nm (200 nm) to 380 nm were simplyaveraged to calculate an average molar absorption coefficient.

The measurement of a reflection spectrum was carried out underconditions of a measurement range of 200 nm to 2500 nm, a sampling rateof 2.0 nm, a measurement rate of medium, and double beamspectrophotometry as a measurement method. Total reflection measurementwas performed to measure specular reflection and diffused reflection.For the measurement on powders, a standard white plate (product name:Spectralon (trademark), manufactured by Labsphere) was used forbackground measurement (baseline setting). The reflection spectrum wasmeasured using the dry powder of the silicon compound-coated iron oxideparticles obtained in each example. For a specific wavelength region,the values of reflectance at a plurality of measurement wavelengths weresimply averaged, thereby giving the average reflectance value. From thereflection spectrum measurement results, hue and saturation weremeasured under the conditions that the colorimetric system was an L*a*b*colorimetric system, the field of view was 2 (deg.), an optical sourcewas D65-2, the color-matching function was JIS Z8701:1999, and a dateinterval was 5 nm. Then, each value of the resulting L*, a*, and b* wassubstituted into the equations of hue H=b*/a* and color saturationC=((a*)²+(b*)²)^(1/2) to calculate both hue and color saturation.

Example 1

Hereinafter, Example 1 describes silicon compound-coated iron oxideparticles in which at least part of the surface of iron oxide particlesprovided as oxide particles is coated with a silicon compound. Using ahigh-speed rotation-type dispersion emulsifier CLEARMIX (product name:CLM-2.2S, manufactured by M Technique Co., Ltd.), an oxide raw-materialliquid (liquid A), an oxide precipitation solvent (liquid B), and asilicon compound raw-material liquid (liquid C) were prepared. UsingCLEARMIX at a rotor rotational speed of 20,000 rpm, the respectiveingredients of the oxide raw-material liquid were stirred andhomogeneously mixed together at a preparation temperature of 40° C. for30 minutes to prepare an oxide raw-material liquid. Also, based on theformulation of the oxide precipitation solvent shown in Example 1 ofTable 1, using CLEARMIX at a rotor rotational speed of 15,000 rpm, therespective ingredients of the oxide raw-material liquid were stirred andhomogeneously mixed together at a preparation temperature of 45° C. for30 minutes to prepare an oxide precipitation solvent. Furthermore, basedon the formulation of the silicon compound raw-material liquid show inExample 1 of Table 1, using CLEARMIX at a rotor speed of 6.000 rpm, therespective ingredients of the silicon compound raw-material liquid werestirred and homogeneously mixed together at a preparation temperature of20° C. for 10 minutes to prepare a silicon compound raw-material liquid.Regarding substances indicated by chemical formulas and abbreviationsdescribed in Table 1, 97 wt % H₂SO₄ used was concentrated sulfuric acid(manufactured by Kishida Chemical Co., Ltd.), NaOH used was sodiumhydroxide (manufactured by KANTOCHEMICAL CO., LTD.), TEOS used wastetraethyl orthosilicate (manufactured by Wako Pure Chemical Industries,Ltd.), and Fe(NO₃)₃.9H₂O used was iron nitrate nonahydrate (manufacturedby KANTOCHEMICAL CO., LTD.).

Subsequently, the prepared oxide raw-material liquid, oxideprecipitation solvent, and silicon compound raw-material liquid weremixed together using a fluid treatment apparatus described in PatentLiterature 6 of the present applicant. Here the fluid treatmentapparatus described in Patent Literature 6 is one described in FIG. 1(B)of the literature. The apparatus used has a concentric annular shapethat surrounds an opening at the center of the processing surface 2,which is configured as a disk in which openings d20 and d30 of secondand third introduction portions are formed in a ring shape. Inparticular, an oxide raw-material liquid as liquid A was introduced fromthe first introduction portion d1 into between the processing surfaces 1and 2, and an oxide precipitation solvent as liquid B was introducedfrom the second introduction portion d2 into between the processingsurfaces 1 and 2 while driving a processing portion 10 at a rotationalspeed of 1,130 rpm to allow the oxide raw materials and the oxideprecipitation solvent to be mixed in a thin film fluid, therebyprecipitating iron oxide particles to be provided as a core between theprocessing surfaces 1 and 2. Then, a silicon compound raw-materialliquid as liquid C was introduced from the third introduction portion d3into between the processing surfaces 1 and 2 to mix it with a mixturefluid that contains iron oxide particles to be provided as a core in thethin film fluid. A silicon compound was precipitated on the surface ofthe iron oxide particles to be provided as a core. Then, a dischargeliquid containing silicon compound-coated iron oxide particles(hereinafter, also referred to as a dispersion of siliconcompound-coated iron oxide particles) from between the processingsurfaces 1 and 2 of the fluid treatment apparatus. Subsequently, thedischarged dispersion of silicon compound-coated iron oxide particleswas collected in a beaker b through a vessel v.

Table 2 represents operating conditions of the fluid treatmentapparatus, average primary particle diameters calculated from the TEMobservation results of the obtained silicon compound-coated iron oxideparticles, the molar ratios of Si/Fe calculated from TEM-EDS analysis,and calculated values calculated from the formulations and introductionflow rates of liquid A, liquid B, and liquid C. The introductiontemperature (liquid feed temperature) and the introduction pressure(liquid feed pressure) of the liquid A shown in Table 2 was the actualtemperature of liquid A under the introduction pressure in the firstintroduction portion d1. Likewise, the introduction temperature ofliquid B is the actual temperature of liquid B under the introductionpressure in the second introduction portion d2. The introductiontemperature of liquid C is the actual temperature of liquid C under theintroduction pressure in the third introduction portion d3.

The measurement of pH was performed using a pH meter of type D-51 madein HORIBA, Ltd. Before the introduction of liquid A, liquid B, andliquid C into the fluid treatment apparatus, the pH vales of theseliquids were measured at room temperature. It was difficult to measureboth the pH of the mixed fluid immediately after mixing the oxideraw-material liquid and the oxide precipitation solvent and the pHimmediately after mixing the fluid containing the core iron oxideparticles and the silicon compound raw-material liquid. Thus, thedispersion of silicon compound-coated iron oxide particles wasdischarged from the apparatus and then collected into beaker b. Then,the pH of the dispersion was measured at room temperature.

From the dispersion of silicon compound-coated iron oxide particles,which was discharged from the fluid treatment apparatus and thencollected into the beaker b, a dried power and a wet cake sample wereprepared. The preparation method was carried out according to aconventional method of this type of treatment. The discharged dispersionof silicon compound-coated iron oxide particles was collected. Thesilicon compound-coated iron oxide particles were then precipitated, anda resulting supernatant was removed. Subsequently, the precipitatedparticles were subjected to three cycles of washing with 100 parts byweight of pure water and precipitation, followed by three cycles ofwashing with pure water and precipitation. After washing the siliconcompound-coated iron oxide particles, a part of wet cake of the siliconcompound-coated iron oxide particles was dried at 25° C. under −0.10 PaGfor 20 hours to give a dried power. The remainder was taken as a wetcake sample.

TABLE 1 Example 1 Formulation of the 1st fluid Formulation of the 2ndfluid (liquid A: Oxide raw material liquid) (liquid B: Oxideprecipitation solvent) Formulation Formulation Raw Raw pH Raw Raw pHmaterial [wt %] material [wt %] pH [° C.] material [wt %] material [wt%] pH [° C.] Fe(NO₃)₃ 2.00 Pure 98.00 1.8 26.6 NaOH 9.00 Pure 91.00 >14— 9H₂O water water Formulation of the 3rd fluid (liquid C: Siliconcompound raw material liquid) Formulation Raw Raw Raw pH material [wt %]material [wt %] material [wt %] pH [° C.] Pure 96.36 97 wt % 2.46 TEOS1.19 <1 — water H₂SO₄

TABLE 2 Example 1 Introduction temperature Shell/Core Introduction flowrate (liquid feed Introduction pressure Si/Fe Average (liquid feed flowrate) temperature) (liquid feed pressure) Discharged [Molar primary[ml/min] [° C.] [MPaG] liquid ratio] particle Liquid Liquid LiquidLiquid Liquid Liquid Liquid Liquid Liquid Temp. Calc. diameter A B C A BC A B C pH [° C.] value EDS [nm] 400 40 50 141 87 86 0.412 0.10 0.2011.02 30.6 0.14 0.14 9.60

FIG. 3 represents the result of mapping with the STEM of siliconcompound-coated iron oxide particles obtained in Example 1, and FIG. 4represents the result of the line analysis at the position indicated bythe broken line in the HAADF image of FIG. 3. As is evident from FIGS. 3and 4, in the silicon compound-coated iron oxide particles obtained inExample 1, some of the particles were observed not entirely covered withsilicon oxide, and silicon compound-coated iron oxide particles in whichpart of the surface of iron oxide particles was covered with a siliconcompound were observed.

The silicon compound-coated iron oxide particles obtained in Example 1were dehydrated by heat treatment with an electric furnace to changefunctional groups contained in the silicon compound-coated iron oxideparticles. The heat treatment conditions were as follows: untreated inExample 1; 200° C. in Example 1-2; 400° C. in Example 1-3; 600° C. inExample 1-4; and 800° C. in Example 1-5. For each heat treatmenttemperature, the duration of heat treatment was 30 minutes. FIG. 1represents the results of mapping with the STEM of the siliconcompound-coated iron oxides obtained in Example 1-5. FIG. 2 representsthe results of line analysis at the position indicated by the brokenline in the HAADF image of FIG. 1.

As illustrated in FIGS. 1 and 2, the silicon compound-coated iron oxideparticles obtained in Example 1-5 were observed as iron oxide particlesin which the entire particles were coated with a silicon compound.

FIG. 5 represents the results of IR measurement of the siliconcompound-coated oxide particles obtained in Example 1 and Example 1-5 bythe ATR method. The IR measurement results of the siliconcompound-coated oxide particles obtained in Example 1-5 can be seen suchthat, as compared with the results of IR measurement on the siliconcompound-coated oxide obtained in Example 1, broad peaks around 1650cm⁻¹ and around 3400 cm⁻¹ are small and broad peaks in the vicinity of800 cm⁻¹ to 1250 cm⁻¹ are shifted toward the higher wavenumbers.

The results obtained by waveform separation peaks at wavenumbers of 100cm⁻¹ to 1250 cm⁻¹ in the IR measurement results of Example 1 or Example1-5 described above are represented in FIG. 6 for Example 1 and FIG. 7for Example 1-5. As is evident from FIGS. 6 and 7, the total area ratioof each peak of the waveform-separated peaks for the M-OH bonds to thetotal peak components of waveform-separated peaks in Example 1-5 isfound to be small as compared with Example 1. In other words, it wasshown that the ratio of M-OH bonds contained in oxide particles ofExample 1-5 is lower than that of the ratio of M-OH bonds contained inoxide particles of Example 1. The results show that a factor thatappears to shift broad peaks in the vicinity of 800 cm⁻¹ to 1250 cm⁻¹toward the higher wavenumbers may be a decrease in the ratio of peakscontained in the silicon compound-coated iron oxide particles,particularly the ratio of peaks waveform-separated to M-OH bond 1 (inthe vicinity of 936 cm⁻¹ in Example 1 and in the vicinity of 912 cm⁻¹ inExample 1-5).

FIG. 8 represents the results of XRD measurement of siliconcompound-coated iron oxide particles obtained in Example 1-5. As isevident from FIG. 8, only the peaks that came from α-Fe₂O₃ were detectedin the XRD measurement. In other words, it was confirmed that a siliconcompound confirmed in the STEM and IR measurements was non-crystalline.

FIG. 9 represents reflection spectra of oxide particles obtained inExample 1 and Examples 1-2 to 1-5 for light rays at wavelengths of 200nm to 2500 nm. First, as is evident from the figure, with respect to thereflectance for the rays of the near-infrared region at wavelengths of780 nm to 2500 nm, the silicon compound-coated oxide particles obtainedin Example 1-5 is higher than the silicon compound-coated oxideparticles obtained in Example 1. Waveform separation was performed onpeaks at wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹ in the IR spectrum. Forthe total area of each of the waveform-separated peaks (ratio of M-OH[%]), descending order is Example 1-5, Example 1-4, Example 1-3, Example1-2, and Example 1. For the average reflectance for light rays atwavelengths of 780 nm to 2500 nm, ascending order is Example 1-5,Example 1-4, Example 1-3, Example 1-2, and Example 1. FIG. 10 representsa graph of the average reflectance for light rays at wavelengths of 780nm to 2500 nm for the ratio of M-OH [%]. FIG. 10 represents, in additionto Example 1 and Examples 1-2 to 1-5, the data of the averagereflectance value for light beams at wavelengths of 780 nm to 2500 nm ofsilicon compound-coated iron oxide particles on which the heat treatmenttemperature was changed to change the ratio of M-OH bonds. As is evidentfrom FIG. 10, the lower the ratio of M-OH, the higher the averagereflectance for light rays at wavelengths of 780 nm to 2500 nm tended tobe observed. In other words, silicon compound-coated iron oxideparticles, which is one kind of the oxide particles of the presentinvention, are the silicon compound-coated iron oxide particles havingas one of the color characteristics the average reflectance for lightrays at wavelengths of 780 nm to 2500 nm controlled by controlling theratio of M-OH bonds contained in the silicon compound-coated iron oxideparticles, preferably having the average reflectance for light rays atwavelengths of 780 nm to 2500 nm enhanced by lowering the ratio of M-OHbonds, and more preferably having the average reflectance value forlight rays at wavelengths of 780 nm to 2500 nm enhanced to 50% bylowering the ratio of M-OH bonds to 8% or more and 14.5% or less. Theuse of such silicon compound-coated iron oxide particles in a coatingcomposition allows the coating composition to be suitably used in apaint to exert an advantageous effect of suppressing a rise intemperature of a coated body irradiated with sunlight.

FIG. 11 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm for the ratio of M-OHbonds contained in silicon compound-coated iron oxide particles, whichwere heat-treated such that an aqueous dispersion of the siliconcompound-coated iron oxide particles obtained in Example 1 was allowedto stand at 100° C. for 0.5 hours, 1.0 hour, and 2.0 hours. The ratio ofM-OH bonds in each treatment time period, which was determined by the IRmeasurement and waveform separation, was follows: 14.8% in Example 1(without treatment); 13.3% in 0.5-hour treatment; 12.6% in 1.0hour-treatment; and 11.1% in 2.0-hour treatment. As is evident from FIG.11, the lower the ratio of M-OH, the higher the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm was observed. In thepresent invention, when the ratio of M-OH bonds contained in the siliconcompound-coated iron oxide particles is controlled by heat treatment,the oxide particles may be in a dry state or may be in a state of beingdispersed in a dispersion medium.

FIG. 12 represents transmission spectra of silicon compound-coated ironoxide particles obtained in Example 1 and Example 1-5 and, forcomparison, a dispersion of iron oxide particles obtained in Example 4described below, which have the surface not coated with a siliconcompound, being dispersed as Fe₂O₃ at a concentration of 0.05% by weightin propylene glycol.

The iron oxide particles, in which the surface thereof was not coatedwith the silicon compound, obtained in Example 4 were produced in thesame manner as in Example 1 to obtain iron oxide particles having thesame particle diameter as in Example 1, except that the third fluid inExample 1 is not used and that the third introduction portion and theopening d30 of the third introduction portion of the fluid treatmentapparatus described in Patent Literature 6 were not formed.

As illustrated in. 12, by changing the ratio of M-OH bonds contained inthe silicon compound-coated iron oxide particles, it is found that theshape of the transmission spectrum changes. Furthermore, it is foundthat the silicon compound-coated iron oxide particles obtained inExample 1 and Example 1-5 have higher transmittance to light rays atwavelengths of 600 nm to 780 m, compared with the iron oxide of Example4 having the surface thereof not coated with a silicon compound. Thesimilar results as in Example 1 and Example 1-5 were obtained forExamples 1-2 to 1-4. In the present invention, the ratio of M-OH bondscontained in the silicon compound-coated iron oxide particles is 9% ormore and 15% or less. In the transmission spectrum of the dispersion inwhich the silicon compound-coated iron oxide particles are dispersed ina dispersion medium, it is preferable that the transmittance for lightrays at a wavelength of 380 nm is 5% or less and the transmittance forlight rays at a wavelength of 600 nm is 80% or more.

Next, silicon compound-coated iron oxide particles were prepared suchthat, at the time of preparing the silicon compound-coated iron oxideparticles in Example 1, the flow rate of the second fluid (liquid B) waschanged to vary the pH of the discharge liquid. Table 3 describes theratio of M-OH [%], which is the area ratio of peaks with respect to thetotal area of each waveform-separated peak after performing waveformseparation on peaks at wavenumbers of 100 cm⁻¹ to 1250 cm⁻¹. The ratioof M-OH bonds was changed by controlling the pH value for theprecipitation of silicon compound-coated oxide particles.

TABLE 3 Introduction temperature Introduction flow rate (liquid feedIntroduction pressure Shell/Core Average (liquid feed flow rate)temperature) (liquid feed pressure) Discharged Si/Fe primary [ml/min] [°C.] [MPaG] liquid [Molar ratio] particle M—OH Liquid Liquid LiquidLiquid Liquid Liquid Liquid Liquid Liquid Temp. Calc. diameter ratioExample A B C A B C A B C pH [° C.] value EDS [nm] [%] 1-6 400 50 50 14187 86 0.402 0.10 0.20 12.17 29.6 0.14 0.14 9.58 14.0 1-7 400 39 50 14187 86 0.396 0.10 0.20 9.42 32.9 0.14 0.14 9.67 14.2 1-8 400 38 50 141 8786 0.382 0.10 0.20 6.87 31.8 0.14 0.14 9.59 13.8

FIG. 13 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm for the ratio of M-OHbonds contained in the silicon compound-coated iron oxide particlesobtained in Examples 1-5 to 1-8. As is evident from FIG. 13, the lowerthe ratio of M-OH, the higher the average reflectance for light rays atwavelengths of 780 nm to 2500 nm tended to be observed as with Example 1to Example 1-5.

FIG. 14 is a graphic diagram illustrating the maximum reflectance forlight rays at wavelengths of 400 nm to 620 nm for the ratio of M-OHbonds contained in silicon compound-coated iron oxide particles obtainedin Example 1 by modification of functional groups contained in thesilicon compound-coated iron oxide particles. As is evident from FIG.14, the silicon compound-coated iron oxide particles obtained by themodification of functional groups of silicon compound in the siliconcompound-coated iron oxide particles in Example 1 are those having themaximum reflectance of 18% or less with respect to light rays atwavelengths of 400 nm to 620 nm of the above silicon compound-coatediron oxide particles in the case that the ratio of M-OH bonds containedin the silicon compound-coated iron oxide particles is in the range of10% or more and 15% or less, exerting the effect of suppressing thereflection of light other than red. Because such a siliconcompound-coated iron oxide particles can reduce the amount of light raysexcept red, it can be suitably used in a coating composition, such as alaminated paint film with red.

FIG. 15 is a graphic diagram illustrating the average reflectance forlight rays at wavelengths of 620 nm to 750 nm for the ratio of M-OHbonds contained in the silicon compound-coated iron oxide particlesobtained in Example 1 by modification of functional groups contained inthe modification of functional groups. As is evident from FIG. 15, inthe case that the ratio of M-OH bonds contained in the siliconcompound-coated iron oxide particles is in the range of 5% or more and13% or less, the average reflectance of the oxide particles for lightrays at wavelengths of 620 nm to 750 nm is 22% or less. Such siliconcompound-coated iron oxide particles are able to reduce the reflectancein the red region. Thus, the silicon compound-coated iron oxideparticles are preferable because, when used for a multilayer coatingfilm, the effect of increasing the difference between highlight andshade is large. Among the examples represented in FIG. 15, the siliconcompound-coated iron oxide particles in which the ratio of M-OH bondscontained therein is 8% more and 9.3% or less or more than 13.3% and 15%or less and the average reflectance of the oxide particles for lightrays at wavelengths of 620 nm to 750 nm is higher than 22% stronglydevelops red color as compared with the silicon compound-coated ironoxide in which the average reflectance thereof for light rays atwavelengths of 620 nm to 750 nm is 22% or less. The particles can besuitably used for reduction of a red pigment separately used for forminga red coating film when used as a red pigment or for a general paint, aswell as suitably used for fine adjustment of color and the like.

FIG. 16 is a graphic diagram illustrating hue in an L*a*b* colorimetricsystem for the ratio of M-OH bonds contained in silicon compound-coatediron oxide particles obtained in Example 1. In addition, Table 4represents hue H of the silicon compound-coated iron oxide particlesobtained in Example 1 and Examples 1-2 to 1-5 and hue H of the ironoxide particles obtained in Example 4. As is evident from Table 4, theratio of the M-OH bonds contained in the iron oxide particles in whichthe surface thereof is not coated with the silicon compound is lower ascompared with the silicon compound-coated iron oxide particles. Inaddition, the hue of the iron oxide particles is out of the range of thehue of silicon compound-coated iron oxide particles. The control of thecolor characteristics by controlling the M-OH bonds of the presentinvention can also be carried out by coating at least a part of thesurface of the particles. It can be understood that the hue of thesilicon compound-coated iron oxide particles cannot be achieved bymerely converting the iron oxide particles into nano-particles. In thesilicon compound-coated iron oxide particles of the present invention,preferably, the ratio of M-OH bonds contained therein is 8% or more and15% or less, and hue H (=b*/a*) in an L*a*b* colorimetric system is inthe range of 0.5 to 0.9.

TABLE 4 Example 1 1-2 1-3 1-4 1-5 4 M—OH ratio [%] 14.8 11.3 10.7 9.99.2 7.8 Hue H (=b*/a*) 0.81 0.72 0.68 0.67 0.58 0.96

FIG. 17 is a graphic diagram that represents, with respect to themeasurement wavelength, an absorption spectrum of a dispersion medium inwhich silicon compound-coated iron oxide particles obtained in Example 1and Example 1-5 of the present invention are dispersed in polypropyleneglycol and an absorption spectrum of a dispersion in which iron oxideparticles obtained in Example 4 are dispersed in polypropylene glycol,and represents a molar absorption coefficient calculated from theconcentration of silicon compound-coated iron oxide particles (as Fe₂O₃)in a dispersion used in the measurement. Furthermore, FIG. 18 is agraphic diagram illustrating the average molar absorption coefficientfor light rays at wave lengths of 190 nm to 380 nm with respect to theratio of M-OH bonds contained in the silicon compound-coated iron oxideparticles obtained in each of Examples 1, 1-3, 1-4, and 1-5.Furthermore, in Table 5, the ratio of M-OH in the siliconcompound-coated iron oxide particles obtained in each of Example 1 andExamples 1-3 to 1-5 and the average molar absorption coefficient thereofat waveforms of 190 nm to 380 nm are represented together with theaverage molar absorption coefficient of the iron oxide particlesobtained in Example 4 at wavelengths of 190 nm to 380 nm.

TABLE 5 Example 1 1-3 1-4 1-5 4 M-OH ratio [%] 14.8 10.7 9.9 9.2 7.8Average molar absorption coefficient [L/(mol · cm)] 2255 2467 2756 3129770 (190-380 nm)

As is evident from FIG. 18 and Table 5, as the M-OH ratio decreased, theaverage molar absorption coefficient at the wavelengths of 190 nm to 380nm tended to increase. As is evident from Table 5, siliconcompound-coated iron oxide particles obtained in Example 1 and Example1-5 have an extremely high average molar absorption coefficient atwavelengths of 190 nm to 380 nm as compared with the iron oxideparticles in which the surface thereof is coated with silicon compound.In the silicon compound-coated iron oxide particles according to therepresent invention, it is preferable that the ratio of M-OH bondscontained in the silicon compound-coated iron oxide particles is 9% ormore and 15% or less, and, in a dispersion in which the siliconcompound-coated oxide particles, an average molar absorption coefficientof the dispersion medium to light rays at wavelengths of 190 nm to 380nm is 2200 L/(mol·cm) or more. As the molar absorption coefficientincreases to this level, the design of the coating or film-likecomposition is facilitated. Simply mixing with a very small amount ofsilicon compound-coated iron oxide can protect the film from ultravioletrays. Utilizing the red coloration of iron oxide furthermore, it ispossible to produce coated products, films, and glass products with highdesign properties of from light skin color to red color.

FIG. 19 represents the reflection spectrum of silicon compound-coatediron oxide particles obtained by, as the modification of functionalgroups of silicon compound-coated oxide particles, reacting a hydroxylgroup and an acetyl group contained in the silicon compound-coated ironoxide particles obtained in Example 1 with each other to provide anacetoxysilyl group to the silicon compound-coated iron oxide particles.Table 6 represents the IR spectrum, the M-OH ratio calculated fromwaveform separation, and the average reflectance of the oxide particlesfor light rays at wavelengths of 780 nm to 2500 nm. In order to give anacetoxysilyl group as an ester group to the silicon compound-coated ironoxide particles obtained in Example 1, the following operation wasperformed on the silicon compound-coated iron oxide particles of Example1-9. First, 1 part by weight of the silicon compound-coated iron oxideparticles obtained in Example 1 was charged into 99 parts by weight ofpropylene glycol (manufactured by Kishida Chemical Co., Ltd.), andsubjected to 1-hour dispersion treatment using a high-speedrotation-type dispersion emulsifier CLEARMIX (product name: CLM-2.2S,manufactured by M Technique Co., Ltd.) at a rotor speed of 20,000 rpm at65° C. to prepare a dispersion. Then, 1 part by weight of aceticanhydride (manufactured by Kishida Chemical Co., Ltd.) and 2 parts byweight of pyridine (manufactured by KANTO CHEMICAL CO., LTD.) were addedto 1 part by weight of the propylene glycol dispersion of the siliconcompound-coated iron oxide particles, and subjected to 1-hour dispersiontreatment using a high-speed rotation-type dispersion emulsifier at arotor speed of 20,000 rpm at 65° C. The resulting treated liquid wascentrifuged at 26,000 G for 15 minutes, and the supernatant was thenseparated to obtain a precipitate. A part of the sediment was dried at−0.10 MPaG at 25° C. for 20 hours to obtain a dried powder. The resultsof the TEM observation confirmed that the silicon compound-coated ironoxide particles obtained in Example 1-9 were substantially the same kindof particles as the silicon compound-coated iron oxide particlesobtained in Example 1.

FIG. 20 is a diagram illustrating the results of FT-IR spectrum(infrared absorption spectrum) measurement of the siliconcompound-coated iron oxide particles obtained in Example 1 and Example1-9. From the FT-IR measurement results of the silicon compound-coatediron oxide particles obtained in Example 1-9, which were prepared byaddition of acetoxysilyl group to the silicon compound-coated iron oxideparticles obtained in Example 1, a broad peak derived from the hydroxylgroup in the vicinity of 2900 cm⁻¹ to 3600 cm⁻¹ observed in the FT-IRmeasurement results of the silicon compound-coated iron oxide particlesobtained in Example 1 was lowered. A new peak was detected in thevicinity of 1450 cm⁻¹ and in the vicinity of 1600 cm⁻¹. It is thoughtthat the acetoxysilyl group was given to the silicon compound-coatediron oxide particles as a result of generation of an ester bond by thereaction of hydroxyl group with acetyl group contained in the siliconcompound-coated iron oxide particles obtained in Example 1. Furthermore,peaks in the vicinity of 800 cm⁻¹ to 1250 cm⁻¹ were changed. In the IRspectra of Example 1 and Example 1-9, waveform separation was performedat wavenumbers in the range of 100 cm⁻¹ to 1250 cm⁻¹ to calculate theratio of M-OH. The results are listed in Table 6 together with theaverage reflectance of the oxide particles for light rays at wavelengthsof 780 nm to 2500 nm. The results of the silicon compound-coated ironoxide particles obtained in Example 1-10 were also shown in Table 6 andFIG. 19 obtained in Example 1-10 under the same conditions except that atemperature of 80° C. and a dispersion treatment time of 2 hour wereemployed in the steps of addition of pyrimidine and acetic anhydride andthe I-hour dispersion treatment at a rotor speed of 20,000 rpm at 65° C.in Example 1-9.

As is evident from FIG. 19 and Table 6, it is found that an acetyl groupwas acted on a hydroxyl group contained in the silicon compound-coatediron oxide particles to cause a decrease in the ratio of M-OH and anincrease in the average reflectance for light rays at wavelengths of 780nm to 2500 nm. As is evident from Table 6, Examples 1-9 and 1-10 causeda lower ratio of M-OH as compared with Example 1, and tended to increasethe average reflectance for light rays at wavelengths of 780 nm to 2500nm. In the present invention, preferable silicon compound-coated oxideparticles are those in which the silicon compound thereof includes anester bond, the ratio of M-OH bonds thereof is 9% or more and 13% orless, and the average reflectance for light rays at wavelengths of 780nm to 2500 nm to be the silicon compound-coated oxide particles of than50%.

TABLE 6 Example 1 1-9 1-10 M-OH ratio [%] 14.8 10.5 9.2 Averagereflectance [%] 48.8 56.9 67.4 (780-2500 nm)

Example 1-11 to Example 1-13

Next, silicon compound-coated iron oxide particles were prepared in thesame manner as in Example 1 except that the dispersion of siliconcompound-coated iron oxide particles, which was discharged from thefluid treatment apparatus and collected in the beaker in Example 1, wasprocessed using a dispersion modifier 100 shown in FIG. 34. Thedispersion modifier 100 is an example of a device that makes thedispersing device and the membrane filter communicate with each other.The dispersion modifier 100 of FIG. 34 is the representative example ofthe device that can be used for controlling the ratio of M-OH bonds inaccordance with the present invention for removing impurities from thedispersion of silicon compound-coated iron oxide particles and adjustingthe pH and conductivity thereof. Specifically, the dispersion modifier100 includes a dispersion-processing device 110, a removal part 120having a membrane filter, and a storage container 13, which areconnected to each other through a piping system. Thedispersion-processing device 110 mainly includes, as main components, adispersion container 101 and a dispersing machine 102 disposed in thedispersion container 101.

The dispersion of silicon compound-coated iron oxide particles, whichwas discharged from the fluid treatment apparatus and collected in thebeaker in Example 1 is provided as a dispersion of siliconcompound-coated iron oxide particles L1 and charged into a storagecontainer 130. Then, a pump 104 is activated to supply the dispersion ofsilicon compound-coated iron oxide particles L1 to a dispersioncontainer 101. The dispersion of silicon compound-coated iron oxideparticles L1 delivered by the pump 104 fills the inside of thedispersion container 101 and overflows. Then, the dispersion is sent tothe removal part 120, and a part thereof is discharged as a filtrate L3together with the crossflow-cleaning liquid L2, and the other partthereof is charged into the storage container 130 again. It ispreferable that the storage container 130 is provided with a stirrer 200for making the concentration of the dispersion uniform. The dispersionof silicon compound-coated iron oxide particles introduced into thestorage container 130 is supplied to the dispersion container 101, andthe dispersion and the removal of impurities are continuously andrepeatedly performed.

The apparatus based on the principle represented in FIG. 34 iseffectively used to modify the dispersion of silicon compound-coatediron oxide particles, thereby allowing the impurities to be released inthe aggregate of silicon compound-coated iron oxide particles containedin the dispersion of silicon compound-coated iron oxide particles;removing the impurities before re-aggregation progresses over time or ina state that more impurities are being present in the liquid of thedispersion; and, in a state that the silicon compound-coated iron oxideparticles are uniformly dispersed, strictly controlling the ratio ofM-OH bonds for each of individual silicon compound-coated iron oxideparticles.

Table 7 represents the conditions for controlling the ratio of M-OHbonds using the dispersion modifier 100 in FIG. 34.

First, 15 kg of pure water (Table 7: (1), pH 5.89 (measurementtemperature: 22.4° C.), conductivity: 0.80 μS/cm (measurementtemperature: 22.4° C.)) was introduced into the storage container 130.Then the pump 104 was activated to supply the pure water to thedispersion container 101 equipped with the dispersing machine 102 (Table7 (3), a high-speed rotation-type dispersion emulsifier CLEARMIX,product name: CLM-2.2S, rotor: RI, screen: S 0.8-48, manufactured by MTechnique Co., Ltd.). The pure water supplied by the pump 104 filled thedispersion container 101 and overflowed therefrom. Then, the pure waterwas fed into a hollow fiber dialyzer (Table 7: (4), film area: 2.2 m²,material: polysulfone, manufactured by Nikisso Co., Ltd.), which wasprovided as a filtration film of the removal part 120 in which purewater was fed as a cross-flow washing liquid at a flow rate of 1.5 L/minat 21° C. (Table 7: (2). pH: 5.89 (measurement temperature: 22.4° C.)),conductivity: 0.80 μS/cm (measurement temperature: 22.4° C.).Subsequently, part of the pure water was discharged as a filtrate L3together with a cross-flow washing liquid, and the remaining part of thepure water was returned to the storage container 130.

Next, the dispersing machine 102 was activated at a rotor speed of20,000 rpm (Table 7: (5), circumferential speed: 31.4 m/s). At the stagewhen pure water was discharged until the pure water in the storagecontainer 130 reached 1 L (ca. 1 kg), 14 L (ca. 14 kg) of the dispersionof silicon compound-coated iron oxide particles (pH: 11.02 (measurementtemperature: 30.6° C.)) was introduced into the storage container 130(Table 7: (6), (7)). The dispersion of silicon compound-coated ironoxide particles was mixed with the pure water circulating in theapparatus, and then circulated from the container to the containerthrough the dispersion-processing device and the membrane filter in amanner similar to the pure water. At this time, the pH of the dispersionof silicon compound-coated iron oxide particles in the storage containerwas 10.88 (measurement temperature: 26.6° C.) (Table 7: 26.6° C.) (Table7: (8)), conductivity: 8120 μS/cm (measurement temperature: 26.6° C.)(Table 7: (9)).

The dispersion of silicon compound-coated iron oxide particles wassubjected to dispersion treatment in the dispersion container 101, andthen fed into the removal part 120 and filtered to discharge a filtratecontaining impurities L3 together with the cross-flow washing liquid.The dispersion of silicon compound-coated iron oxide particles fed bythe pump 104 at a flow rate of 8.8 L/min (Table 7: (10)) was returned tothe storage container 130 at a flow rate of 7.3 L/min (Table 7 (11)).Thus, the filtrate L3 that contains impurities was successivelydischarged at a flow rate of 1.5 L/min through the membrane filter ofthe removal part 120.

At the stage when the dispersion of silicon compound-coated iron oxideparticles in the storage container 130 was concentrated up to 1.5 L (ca.1.5 kg), 13.5 L (ca. 13.5 kg) of pure water (pH: 5.89 (measurementtemperature: 22.4° C.), conductivity: 0.801 μS/cm (measurementtemperature: 22.4° C.) was introduced into the storage container 130(Table 7: (13), (14)). The state of being activated was kept andcontinued during and before and after the introduction to removeimpurities in the dispersion of silicon compound-coated iron oxideparticles. The concentration of the silicon compound-coated iron oxideparticles in the dispersion thereof varied from 0.4 to 2.0 wt % duringthe period between the enrichment (1.5 L of the concentrated dispersion)and the dilution (15 L of the diluted dispersion) 2.0 wt % (Table 7:(15)). Pressure gauges in FIG. 34 indicated 0.10 MPaG in two Pa, 0.15MPaG in Pb, and 0.02 MPaG in Pc (Table 7: (16), (17), and (18)). Theimmediately preceding transport path from the dispersion container 101to the removal part 120 had a path length (Lea) of 0.3 m (Table 7: (19))and a pipping inner diameter (Leb) of 0.0105 m (Table 7: 20)). The flowvelocity of the dispersion of silicon compound-coated iron oxideparticles in the immediately preceding transport path was 1.2 m/sec(Table 7: (21)). In addition, the time TI until the removal ofimpurities from the dispersion container 101 was started by the removalpart 120 was 0.24 sec (0.24 sec) (Table 7: (22)) and was thus consideredto be 3 seconds or less. Furthermore, a thermometer (not shown) disposedin the dispersion container 101 indicated a temperature of 23 to 26° C.(Table 7: (23)). The temperature of the dispersion of siliconcompound-coated iron oxide particles in the storage container 130 was 23to 26° C. (Table 7: (24)). For conductivity measurement, an electricalconductivity meter, model number ES-51 manufactured by HORIBA, Ltd., wasused (Table 7: (25)).

Both the procedures for dispersing the dispersion of siliconcompound-coated iron oxide particles and procedures for removal ofimpurities in the dispersion of silicon compound-coated iron oxideparticles were carried out repeatedly until the pH of the dispersion ofsilicon compound-coated iron oxide particles reached 6.91 (measurementtemperature: 24.6° C.) and the conductivity thereof reached 7.14 μS/cm.The impurities contained in the aggregates of silicon compound-coatediron oxide particles were also removed. Thus, each of the siliconcompound-coated iron oxide particles in the dispersion thereof wasmodified.

TABLE 7 Examples 1-11 Processing solution Silicon compound-coated ironoxide particle dispersion liquid  (1) 1st amount of solution chargedinto container Type: Pure water 130 pH 5.89 (measurement temperature:22.4° C.) Conductivity 0.80 μS/cm (measurement temperature 22.4° C.)Input: 15 kg  (2) Type, flow rate, and temperature of cross flow Type:Pure water cleaning liquid pH 5.89 (measurement temperature: 22.4° C.)Conductivity 0.80 μS/cm (measurement temperature 22.4° C.) Flow rate:1.5 L/min, 21° C.  (3) Dispersing machine 102 CLEARMIX (product name:CLM-2. 2S, rotor: R1, screen: S 0.8-48, manufactured by M Technique Co.,Ltd.)  (4) Removal part 120 Hollow fiber type dialyzer PN-220 (filmarea: 2.2 m², material: polysulfone), manufactured by Nikkiso Co., Ltd. (5) Rotor speed 20,000 rpm (peripheral speed: 31.4 m/S)  (6) Start ofcharging oxide particle dispersion When the first pure water inside thevessel 130 has been reduced to 1 L  (7) Input of oxide particledispersion into oxide 14 L (ca. 14 kg) container 130  (8) pH of oxideparticle dispersion liquid inside 10.88 (measuring temperature: 26.6°C.) vessel 130  (9) Conductivity of oxide particle dispersion liquid8120 μS/cm (measurement temperature: 26.6° C.) inside the vessel 130(10) Flow rate of pump 104 8.8 L/min (11) Flow rate oxide particledispersion liquid is 7.3 L/min returned to storage container 130 (12)Discharge amount (calculated value) of filtrate 1.5 L/min L3 by removalpart 120 (13) Timing of introduction of diluent into container When thedispersion amount in storage container 130 is 130 concentrated to 1.5 L(14) Type and input of 2nd different dilution to Type: Pure waterstorage container 130 pH 5.89 (measurement temperature: 22.4° C.)Conductivity 0.80 μS/cm (measurement temperature 22.4° C.) Input: 13.5 L(ca. 13.5 kg) (15) Concentration of oxide particles in oxide 0.4 wt % to2.0 wt % particle dispersion (16) Pressure gauge Pa: Both of two are0.10 MPaG (17) Pressure gauge Pb: 0.15 MPaG (18) Pressure gauge pc: 0.02M PaG (19) Path length (Lea) 0.3 m (20) Pipping inner diameter (Leb)0.0105 m (21) Flow velocity of oxide particle dispersion liquid 1.2m/sec in immediately preceding transport path (22) Time T1 until removalpart 120 starts removal 0.24 sec of impurities from dispersion container101 (23) Thermometer placed in the dispersion 23° C. to 26° C. container101 (24) Temperature of oxide particle dispersion 23° C. to 26° C. (25)Conductivity measuring machine Electrical conductivity meter, modelnumber ES-51 manufactured by HORIBA, Ltd.

By changing the treatment temperature in the modification of thedispersion of silicon compound-coated iron oxide particles shown in (23)and (24) of Table 7, silicon compound-coated iron oxide particles havingdifferent ratios of M-OH in Examples 1-11 to 1-13 were prepared. Table 8represents, together with the results of Example 1, the treatmenttemperature for modifying the dispersion of silicon compound-coated ironoxide particles, the ratio of M-OH in the resulting siliconcompound-coated iron oxide particles, the average reflectance valuesthereof at wavelengths of 780 nm to 2500 nm, and the molar absorptioncoefficients thereof at wavelengths of 190 nm to 380 nm.

TABLE 8 Example 1 1-11 1-12 1-13 Treatment temperature — 23-26 43-4659-61 (Table 7: (23)) [° C.] Treatment temperature — 23-26 43-46 59-61(Table 7: (24)) [° C.] M-OH ratio [%] 14.8 13.8 10.1 9.4 Averagereflectance [%] 48.8 54.2 60.1 68.4 (780-2500 nm) Average molarabsorption 2255 2314 2614 2946 coefficient [L/(mol · cm)] (190-380 nm)

As is evident from Table 8, the lower the ratio of M-OH the higher theaverage reflectance of the oxide particles at wavelengths of 780 nm to2500 nm and the molar absorption coefficient at wavelengths of 190 nm to380 nm tended to be observed. Thus, it is found that the colorcharacteristics of the oxide particles can be controlled by controllingthe ratio of M-OH.

Example 2

Example 2 describes, as oxide particles, silicon compound-coated zincoxide particles in which at least a part of the surface of zinc oxideparticles is coated with a silicon compound. An oxide precipitationsolvent (liquid A), an oxide raw-material liquid (liquid B), and asilicon compound raw-material liquid (liquid C) were prepared using ahigh-speed rotation-type dispersion emulsitier CLERMIX (product name:CLM-2.2S, manufactured by M Technique Co., Ltd.). Specifically, based onthe formulation of the oxide raw-material liquid shown in Example 2 inTable 9, the ingredients of the oxide raw-material liquid werehomogeneously mixed by stirring them at 20,000 rpm for 30 minutes at apreparation temperature of 40° C. using CLEARMIX to prepare an oxideraw-material liquid. Based on the formulation of the oxide precipitationsolvent shown in Example 2 in Table 9, the ingredients of the oxideraw-material liquid were homogeneously mixed by stirring them at 15,000rpm for 30 minutes at a preparation temperature of 45° C. using CLEARMIXto prepare an oxide precipitation solvent. Furthermore, based on theformulation of the oxide precipitation solvent shown in Example 2 inTable 9, the ingredients of the oxide raw-material liquid werehomogeneously mixed by stirring them at 15,000 rpm for 30 minutes at apreparation temperature of 45° C. using CLEARMIX to prepare an oxideprecipitation solvent. Furthermore, based on the formulation of asilicon compound shown in Example 2 in Table 9, the ingredients ofsilicon compound-coated iron oxide particles were homogeneously mixed bystirring them at 6,000 rpm for 10 minutes at a preparation temperatureof 20° C. using CLEARMIX to prepare silicon compound-coated iron oxideparticles.

Regarding substances indicated by chemical formulas and abbreviationsdescribed in Table 9, 97 wt % H₂SO₄ used was concentrated sulfuric acid(manufactured by Kishida Chemical Co., Ltd.), KOH used was potassiumhydroxide (manufactured by KANTOCHEMICAL CO., LTD.), TEOS used wastetraethyl orthosilicate (manufactured by Wako Pure Chemical Industries,Ltd.), and ZnO used was zinc oxide (manufactured by KANTOCHEMICAL CO.,LTD.).

Subsequently, the prepared oxide raw-material liquid, oxideprecipitation solvent, and silicon compound raw-material liquid weremixed together using a fluid treatment apparatus described in PatentLiterature 6 of the present applicant. A method for treating each fluidand a method for collecting the treated liquid were carried out in amanner similar to Example 1.

Table 10 represents, as with Example 1, the operating conditions of thefluid treatment apparatus, the average primary particle diametercalculated from the TEM observation result of the obtained siliconcompound-coated zinc oxide particles, and the molar ratio of Si/Zncalculated from the TEM-EDS analysis, as well as calculated valuescalculated based on the formulations and introduced flow rates of liquidA, liquid B, and liquid C. The procedures for pH measurement, analysis,and particle-washing were also carried out in the same manner as inExample 1.

TABLE 9 Example 2 Formulation of the 1st fluid Formulation of the 2ndfluid (liquid A: Oxide precipitation solvent) (liquid B: Oxide rawmaterial liquid) Formulation Formulation Raw Raw pH Raw Raw Raw pHmaterial [wt %] material [wt %] pH [° C.] material [wt %] material [wt%] material [wt %] pH [° C.] 97 wt % 6.29 MeOH 93.71 <1 — ZnO 3.00 KOH46.56 Pure 50.44 >14 — H₂SO₄ water Formulation of the 3rd fluid (liquidC: Silicon compound raw material liquid) Formulation Raw Raw Raw pHmaterial [wt %] material [wt %] material [wt %] pH [° C.] MeOH 88.12 35%10.22 TEOS 1.66 <1 — HCl

TABLE 10 Example 2 Introduction temperature Introduction flow rate(liquid feed Introduction pressure Shell/Core Average (liquid feed flowrate) temperature) (liquid feed pressure) Discharged Si/Zn primary[ml/min] [° C.] [MPaG] liquid [Molar ratio] particle Liquid LiquidLiquid Liquid Liquid Liquid Liquid Liquid Liquid Temp. Calc. diameter AB C A B C A B C pH [° C.] value EDS [nm] 575 50 75 28 25 25 0.108 0.100.10 13.61 35.7 0.32 0.32 14.10

FIG. 21 represents the results of mapping with the STEM of the siliconcompound-coated zinc oxide particles obtained in Example 2. FIG. 22represents the results of line analysis at the position indicated by thebroken line in the HAADF image of FIG. 21. As is evident from FIGS. 21and 22, the silicon compound-coated zinc oxide particles obtained inExample 2 were those in which the particles were not entirely coatedwith a silicon compound. The silicon compound-coated zinc oxideparticles having their surfaces partially coated with the siliconcompound were also observed.

The silicon compound-coated zinc oxide particles obtained in Example 2were subjected to heat treatment with an electric furnace to modify thefunctional groups contained in the silicon compound-coated zinc oxideparticles. The heat treatment conditions were as follows: untreated inExample 2; 200° C. in Example 2-2; 400° C. in Example 2-3; and 600° C.in Example 2-4. For each heat treatment temperature, the duration ofheat treatment was 30 minutes. FIG. 23 represents the results of mappingwith the STEM of the silicon compound-coated zinc oxide particlesobtained in Example 2-4. FIG. 24 represents the results of line analysisat the position indicated by the broken line in the HAADF image of FIG.23. As is evident from FIGS. 23 and 24, the silicon compound-coated zincoxide particles obtained in Example 2-4 were observed as the zinc oxideparticles entirely coated with zinc oxides.

FIG. 25 represents the reflectance spectra of the siliconcompound-coated zinc oxide particles obtained in Example 2 and Examples2-2 to 2-4 and, for comparison, zinc oxide particles obtained in Example5, which have the surface not coated with a silicon compound, for lightrays at wavelengths of 200 nm to 2500 nm.

The zinc oxide particles obtained in Example, which have the surface notcoated with a silicon compound, 5 were produced in the same manner as inExample 2 to obtain zinc oxide particles having the same particlediameter as in Example 2, except that the third fluid in Example 2 isnot used and that the third introduction portion and the opening d30 ofthe third introduction portion of the fluid treatment apparatusdescribed in Patent Literature 6 were not formed.

As is evident from FIG. 25, with respect to the reflectance for the raysof the near-infrared region at wavelengths of 780 nm to 2500 nm, thesilicon compound-coated zinc oxide particles obtained in Example 2-4 ishigher than the silicon compound-coated oxide particles obtained inExample 2. Waveform separation was performed on peaks at wavenumbers of100 cm⁻¹ to 1250 cm⁻¹ in the IR spectrum. For the total area of each ofthe waveform-separated peaks (ratio of M-OH [%]), descending order isExample 2-4, Example 2-3, Example 2-2, and Example 2. For the averagereflectance of the oxide particles for light rays at wavelengths of 780nm to 2500 nm, ascending order is Example 2-4, Example 2-3, Example 2-2,and Example 2. FIG. 26 represents a graph of the average reflectance forlight rays at wavelengths of 780 nm to 2500 nm for the ratio of M-OH[%]. As is evident from FIG. 26, the lower the ratio of M-OH, the higherthe average reflectance of the oxide particles for light rays atwavelengths of 780 nm to 2500 nm tended to be observed. Furthermore, inTable 11, the ratio of M-OH in the silicon compound-coated iron oxideparticles obtained in each of Example 2 and Examples 2-2 to 2-4 and theaverage molar absorption coefficient thereof at waveforms of 780 nm to2500 nm are represented together with the average molar absorptioncoefficient of the zinc oxide particles obtained in Example 4 atwavelengths of 780 nm to 2500 nm.

TABLE 11 Example 2 2-2 2-3 2-4 5 M-OH ratio [%] 41.3 38.6 35.4 31.3 11.8Average reflectance [%] 56.4 72.8 76.0 79.3 68.3 (780-2500 nm)

As is evident from Table 11, silicon compound-coated zinc oxideparticles obtained in Example 2 and Example 2-4 have a high averagereflectance value at wavelengths of 780 nm to 2500 nm as compared withthe zinc oxide particles in which the surface thereof is not coated witha silicon compound. With respect to the silicon compound-coated zincoxide particles according to the present invention, preferably, theratio of M-OH bonds contained in the silicon compound-coated zinc oxideparticles is 30% or more and 39% or less, and the average reflectance ofthe oxide particles for light rays at wavelengths of 780 nm to 2500 nmis 72% or more. The use of such silicon compound-coated zinc oxideparticles in a coating composition allows the coating composition to besuitably used in a paint to exert an advantageous effect of suppressinga rise in temperature of a coated body irradiated with sunlight.

FIG. 27 represents the reflectance spectra of the siliconcompound-coated zinc oxide particles obtained in Example 2 and Examples2-2 to 2-4 and zinc oxide particles obtained in Example 4 for light raysat wavelengths of 200 nm to 780 nm. The ratio of M-OH bonds contained insilicon compound-coated zinc oxide particles was changed, and as aresult a change was observed in an absorption region at wavelengths of340 nm to 380 nm. Also, in the silicon compound-coated zinc oxideparticles obtained in Example 2-3 and 2-4, the ratio of M-OH bondsincluded was 30% or more and 36% or less and the reflectance thereofreached 15% at a wavelength of 375 nm or more. Thus, because of theabsorption of light in a wider ultraviolet region, such siliconcompound-coated zinc oxide particles are suitable for a film-likecomposition used in a coating composition, glass, or the like forultraviolet shielding. Table 12 represents the ratio of M-OH bondscontained in the silicon compound-coated zinc oxide particles obtainedin each of Example 2 and Example 2-2 to Example 2-4 and the averagereflectance value thereof for light rays at wavelengths of 380 nm to 780nm in wavelength.

TABLE 12 Example 2 2-2 2-3 2-4 5 M-OH ratio [%] 41.3 38.6 35.4 31.3 11.8Average reflectance [%] 89.0 86.4 82.6 83.5 79.9 (380-780 nm)

In the silicon compound-coated zinc oxide particles obtained in Example2 and 2-2, the ratio of M-OH bonds included was 38% or more and 42% orless and the average reflectance value was 86% or more for light rays ata wavelength of 780 nm. Thus, because of reflecting light over theentire visible region, such silicon compound-coated zinc oxide particlescan be suitably used for white pigments.

FIG. 28 represents a graph of color saturation C(=((a*)²+(b*)²)^(1/2))in an L*a*b* colorimetric system with respect to the ratio of M-OH bondscontained in the silicon compound-coated iron oxide particles. As isevident from FIG. 28, the higher the ratio of M-OH bonds, the lower thecolor saturation tended. In the present invention, preferably, the ratioof M-OH bonds contained in the silicon compound-coated zinc oxideparticles is 31% or more and 39% or less, and color saturationC(=((a*)²+(b*)²)^(1/2)) in an L*a*b* colorimetric system is in the rangeof 0.5 to 13.

FIG. 29 represents a graph of L* values in an L*a*b* colorimetric systemwith respect to the ratio of M-OH bonds contained in the siliconcompound-coated iron oxide particles. As is evident from FIG. 29, thehigher the ratio of M-OH bonds, the lower the L* value tended. In thepresent invention, preferably, the silicon compound-coated zinc oxideparticles have the ratio of M-OH bonds contained therein of 31% or moreand 39% or less, color saturation C(=((a*)²+(b*)²)^(1/2)) in an L*a*b*colorimetric system in the range of 0.5 to 13, and an L* value in theL*a*b* colorimetric system in the range of 95 to 97. Thus, the siliconcompound-coated zinc oxide particles have high whiteness and cansuitably be used as a white pigment.

FIG. 30 represents transmission spectra of dispersions in which siliconcompound-coated iron oxide particles obtained in Examples 2 and Example2-2 to 2-4 and zinc oxide particles obtained in Example 5 wererespectively dispersed in propylene glycol as ZnO at a concentration of0.011% by weight in propylene glycol. Furthermore, Table 13 representsthe ratio of M-OH in the silicon compound-coated iron oxide particlesobtained in each of Example 2 and Example 2-2 to 2-4 and the averagetransmittance for light rays at wavelengths of 380 nm to 780 nm in thetransmission spectrum.

TABLE 13 Example 2 2-2 2-3 2-4 5 M—OH ratio [%] 41.3 38.6 35.4 31.3 11.8Average transmittance [%] 95.7 92.4 91.1 89.9 78.5 (380-780 nm)

In Example 2 and Examples 2-2 to 2-4, the ratio of M-OH bonds decreases,while the edge of the absorption in a region at a wavelength of 380 nmor less is evidently shifted to the longer wavelength side. Furthermore,as is evident from the table, the silicon compound-coated zinc oxideparticles obtained in Example 2 and Example 2-4 have highertransmittance at wavelengths of 380 nm to 780 nm than the zinc oxideparticles obtained in Example 5, and efficiently absorb light rays atwavelengths of 200 nm to 380 nm, the ultraviolet region, as well as hightransparency. In the present invention, the ratio of M-OH bonds includedin the silicon compound-coated zinc oxide particle mentioned above is38% or more and 42% or less. In the transmission spectrum of thedispersion in which the silicon compound-coated zinc oxide particles aredispersed in a dispersion medium, it is preferable that thetransmittance for light rays at a wavelength of 340 nm is 10% or lessand the average transmittance for light rays at wavelengths of 380 nm to780 nm is 92% or more. Thus, such silicon compound-coated zinc oxideparticles are suitable for providing a coating composition having thegood balance between the ability of absorbing ultraviolet rays atwavelengths of 380 nm or less and the transparency when the oxideparticles are used for cosmetics, such as lipsticks, foundations,sunscreen agents, and a coating composition intended to be applied tothe skin, as well as a film-like composition used for a coating film,coating body, glass, or the like. Further, from the transmissionspectrum of the silicon compound-coated oxide obtained in each ofExamples 2-3 and 2-4, the absorption in an ultraviolet region atwavelengths of 200 nm to 380 nm is shifted to the longer wavelength sideas compared with Example 2. In the present invention, preferably, theratio of M-OH bonds contained in silicon compound-coated zinc oxideparticles is 30% or more and 36% or less, and the reflectance thereofbecomes 15% at a wavelength of 375 nm or more. Thus, light rays in anultraviolet region at wavelengths of 200 nm to 380 nm can be broadlyabsorbed.

FIG. 31 represents a graph of molar absorption coefficients calculatedfrom: the results of absorption spectrum measurement of the dispersionsin which silicon compound-coated iron oxide particles obtained inExample 2 and Examples 2-2 to 2-4 and zinc oxide particles obtained inExample 5 were respectively dispersed in propylene glycol; and theconcentrations of silicon compound-coated zinc oxide particles (as ZnO)in the dispersions used in the measurement. Table 14 represents theratio of M-OH in the silicon compound-coated zinc oxide particlesobtained in each example and the molar absorption coefficient thereof atwavelengths of 200 nm to 380 nm together with the molar absorptioncoefficient of zinc oxide particles obtained in Example 5 at wavelengthsof 200 nm to 380 nm.

TABLE 14 Example 2 2-2 2-3 2-4 5 M—OH ratio [%] 41.3 38.6 35.4 31.3 11.8Average molar absorption 951 943 1038 1040 623 coefficient [L/(mol ·cm)] (200-380 nm)

As is evident from Table 14, the lower the ratio of M-OH, the higher themolar absorption coefficient tended to be observed. As is evident fromthe table, furthermore, the silicon compound-coated zinc oxide particlesobtained in Example 2 and Example 2-4 have a high molar absorptioncoefficient at wavelengths of 200 nm to 380 nm as compared with the zincoxide particles obtained in Example 5. In the present invention, theratio of M-OH bonds contained in silicon compound-coated zinc oxideparticles is 30% or more and 42% or less. In the dispersion in which thesilicon compound-coated zinc oxide particles are dispersed in thedispersion medium, the silicon compound-coated zinc oxide particlespreferably has a molar absorption coefficient of 700 L/(mol·cm) or morefor light rays at wavelengths of 200 nm to 380 nm. As a result, it ispossible to efficiently absorb light rays at wavelengths of 200 nm to380 nm, which correspond to ultraviolet rays of UVA, UVB, and UVC. Thus,such silicon compound-coated zinc oxide particles can be suitable forattaining a further increase in transparency while attaining a decreasein the amount used when used for a coating or film-like composition.

Example 2-5 to Example 2-7

Subsequently, from the dispersion of silicon compound-coated zinc oxideparticles discharged from the fluid treatment apparatus and collected inthe beaker in the Example 2, silicon compound-coated zinc oxideparticles were prepared in a manner similar to Example 1 except that thedispersion was subjected to the dispersion modifier 100 shown in FIG.34. Table 15 represents the conditions for controlling the ratio of M-OHbonds in the silicon compound-coated zinc oxide particles using thedispersion modifier 100 in FIG. 34. Excepting of the contents of Table5, silicon compound-coated zinc oxide particles with the controlledratio of M-OH bonds were prepared in a manner similar to Example 1-11 toExample 1-13.

Both the procedures for dispersing the dispersion of siliconcompound-coated iron oxide particles and procedures for removal ofimpurities in the dispersion of silicon compound-coated iron oxideparticles were carried out repeatedly until the pH of the dispersion ofsilicon compound-coated iron oxide particles reached 7.02 (measurementtemperature: 23.1° C.) and the conductivity thereof reached 0.06 μS/cm.The impurities contained in the aggregates of silicon compound-coatediron oxide particles were also removed. Thus, each of the siliconcompound-coated iron oxide particles in the dispersion thereof wasmodified.

TABLE 15 Examples 2-5 Processing solution Silicon compound-coated zincoxide particle dispersion liquid  (1) 1st amount of solution chargedinto container Type: MeOH 130 pH 7.00 (measurement temperature: 23.5°C.) Conductivity 0.01 μS/cm (measurement temperature 23.5° C.) Input: 15L (ca. 12 kg)  (2) Type, flow rate, and temperature of cross flow Type:MeOH cleaning liquid pH 7.00 (measurement temperature: 23.5° C.)Conductivity 0.01 μS/cm (measurement temperature 23.5° C.) Flow rate:0.7 L/min, 24° C.  (3) Dispersing machine 102 CLEARMIX (product name:CLM-2. 2S, rotor: R1, screen: S 0.8-48, manufactured by M Technique Co.,Ltd.)  (4) Removal part 120 Hollow fiber type dialyzer PN-220 (filmarea: 2.2 m², material: polysulfone), manufactured by Nikkiso Co., Ltd. (5) Rotor speed 10,000 rpm (peripheral speed: 15.7 m/S)  (6) Start ofcharging oxide particle dispersion When the first pure water inside thevessel 130 has been reduced to 1 L  (7) Input of oxide particledispersion into oxide 15 L (ca. 12 kg) container 130  (8) pH of oxideparticle dispersion liquid inside more than 14 (measuring temperature:23.2° C.) vessel 130  (9) Conductivity of oxide particle dispersionliquid 3636 μS/cm (measurement temperature: 23.2° C.) inside the vessel130 (10) Flow rate of pump 104 8.8 L/min (11) Flow rate oxide particledispersion liquid is 7.3 L/min returned to storage container 130 (12)Discharge amount (calculated value) of filtrate 1.5 L/min L3 by removalpart 120 (13) Timing of introduction of diluent into container When thedispersion amount in storage container 130 is 130 concentrated to 1.5 L(14) Type and input of 2nd different dilution to Type: MeOH storagecontainer 130 pH 7.00 (measurement temperature: 23.5° C.) Conductivity0.01 μS/cm (measurement temperature 23.5° C.) Flow rate: 0.7 L/min, 24°C. (15) Concentration of oxide particles in oxide 1.0 wt % to 10.0 wt %particle dispersion (16) Pressure gauge Pa: Both of two are 0.10 MPaG(17) Pressure gauge Pb: 0.15 MPaG (18) Pressure gauge Pc: 0.02 MPaG (19)Path length (Lea)   0.3 m (20) Pipping inner diameter (Leb) 0.0105 m(21) Flow velocity of oxide particle dispersion liquid 1.2 m/sec inimmediately preceding transport path (22) Time T1 until removal part 120starts removal 0.24 sec of impurities from dispersion container 101 (23)Thermometer placed in the dispersion 23° C. to 24° C. container 101 (24)Temperature of oxide particle dispersion 23° C. to 24° C. (25)Conductivity measuring machine Electrical conductivity meter, modelnumber ES-51 manufactured by HORIBA, Ltd.

By changing the treatment temperature in the modification of thedispersion of silicon compound-coated iron oxide particles shown in (23)and (24) of Table 15, silicon compound-coated iron oxide particleshaving different ratios of M-OH in Examples 2-5 to 2-7 were prepared.Table 16 represents, together with the results of Example 2, thetreatment temperature for modifying the dispersion of siliconcompound-coated iron oxide particles, the ratio of M-OH in the resultingsilicon compound-coated iron oxide particles, the average reflectancevalues thereof at wavelengths of 780 nm to 2500 nm, the averagereflectance values thereof at wavelengths of 380 nm to 780 nm, thetransmittances thereof at wavelengths 380 nm to 780 nm, and the molarabsorption coefficients thereof at wavelengths of 200 nm to 380 nm.

TABLE 16 Example 2 2-5 2-6 2-7 Treatment temperature — 23-24 35-37 45-48(Table 15: (23)) [° C.] Treatment temperature — 23-24 35-37 45-48 (Table15: (24)) [° C.] M—OH ratio [%] 41.3 39.2 38.6 36.6 Average reflectance[%] 56.4 70.4 74.3 75.3 (780-2500 nm) Average reflectance [%] 89.0 87.486.4 84.3 (380-780 nm) Average transmittance [%] 95.7 93.4 92.3 91.7(380-780 nm) Average molar absorption 951 965 969 1020 coefficient[L/(mol · cm)] (200-380 nm)

As is evident from FIG. 16, the lower the ratio of M-OH, the higher theaverage reflectance values thereof at wavelengths of 780 nm to 2500 nm,the average reflectance values thereof at wavelengths of 780 nm to 2500nm, the transmittances thereof at wavelengths 380 nm to 780 nm, and themolar absorption coefficients thereof at wavelengths of 200 nm to 380 nmtended to be observed. Thus, it is found that the color characteristicsof the oxide particles can be controlled by controlling the ratio ofM-OH.

Example 3

Example 3 describes silicon compound-coated cerium oxide particles inwhich at least a part of the surface of cerium oxide particles is coatedwith a silicon compound. An oxide precipitation solvent (liquid A), anoxide raw-material liquid (liquid B), and a silicon compoundraw-material liquid (liquid C) were prepared using a high-speedrotation-type dispersion emulsifier CLERMIX (product name: CLM-2.2S,manufactured by M Technique Co., Ltd.). Based on the formulation of theoxide raw-material liquid shown in Table 17 of Example 3, theingredients of the oxide raw-material liquid were homogeneously mixed bystirring them at a rotor speed of 20,000 rpm for 30 minutes at apreparation temperature of 45° C. using CLEARMIX to prepare an oxideraw-material liquid. Further, based on the formulation of the oxideprecipitation solvent shown in Example 3 of Table 17, the ingredients ofthe oxide precipitation solvent were homogeneously mixed by stirringthem at 15,000 rpm for 30 minutes at a preparation temperature of 40° C.using CLEARMIX to prepare an oxide precipitation solvent. Further, basedon the formulation of the silicon compound raw-material liquid shown inExample 3 of Table 17, the ingredients of the silicon compoundraw-material liquid were homogeneously mixed by stirring them at 6,000rpm for 10 minutes at a preparation temperature of 20° C. using CLEARMIXto prepare a silicon compound raw-material liquid.

Regarding substances indicated by chemical formulas and abbreviationsdescribed in Table 17, DAME used was dimethyl aminoethanol (manufacturedby Kishida Chemical Co., Ltd.), 60 wt % HNO₃ used was concentratednitric acid (manufactured by Kishida Chemical Co., Ltd.), Ce(NO₃)₃.6H₂Owas cerium (III) nitrate hexahydrate (manufactured by Wako Pure ChemicalIndustries, Ltd.), and TEOS was tetraethylorthosilicate (Wako PureChemical Industries, Ltd.).

Subsequently, the prepared oxide raw-material liquid, oxideprecipitation solvent, and silicon compound raw-material liquid weremixed together using a fluid treatment apparatus described in PatentLiterature 6 of the present applicant. A method for treating each fluidand a method for collecting the treated liquid were carried out in amanner similar to Example 1.

Table 18 represents, as with Example 1, the operating conditions of thefluid treatment apparatus, the average primary particle diametercalculated from the TEM observation result of the obtained siliconcompound-coated cerium oxide particles, and the molar ratio of Si/Cecalculated from the TEM-EDS analysis, as well as calculated valuescalculated based on the formulations and introduced flow rates of liquidA, liquid B, and liquid C. The procedures for pH measurement, analysis,and particle-washing were also carried out in the same manner as inExample 1.

TABLE 17 Example 3 Formulation of the 1st fluid Formulation of the 2ndfluid (liquid A: Oxide precipitation solvent) (liquid B: Oxide rawmaterial liquid) Formulation Formulation Raw Raw pH Raw Raw pH material[wt %] material [wt %] pH [° C.] material [wt %] material [wt %] pH [°C.] DMAE 1.40 Pure 98.60 11.4 26.7 Ce(NO₃)₃ 9.00 Pure 91.00 3.2 29.0water 6H₂O water Formulation of the 3rd fluid (liquid C: Siliconcompound raw material liquid) Formulation Raw Raw Raw pH material [wt %]material [wt %] material [wt %] pH [° C.] Pure 99.49 60% 0.01 TEOS 0.403.0 25.1 water HNO₃

TABLE 18 Example 3 Introduction temperature Introduction flow rate(liquid feed Introduction pressure Shell/Core Average (liquid feed flowrate) temperature) (liquid feed pressure) Discharged Si/Ce primary[ml/min] [° C.] [MPaG] liquid [Molar ratio] particle Liquid LiquidLiquid Liquid Liquid Liquid Liquid Liquid Liquid Temp. Calc. diameter AB C A B C A B C pH [° C.] value EDS [nm] 100 40 50 134 83 27 0.296 0.100.10 7.33 22.9 0.12 0.12 5.26

FIG. 32 represents a TEM photograph of silicon compound-coated ceriumoxide particles obtained in Example 3. The silicon compound-coatedcerium oxide particles obtained in Example 3 were those in which theparticles were not entirely coated with a silicon compound. The siliconcompound-coated cerium oxide particles having their surfaces partiallycoated with the silicon compound were also observed.

The silicon compound-coated cerium oxide particles obtained in Example 3were subjected to heat treatment with an electric furnace to modify thefunctional groups contained in the silicon compound-coated cerium oxideparticles. The heat treatment conditions were as follows: untreated inExample 3; 200° C. in Example 3-2; 400° C. in Example 3-3; and 600° C.in Example 2-4. For each heat treatment temperature, the duration ofheat treatment was 30 minutes.

FIG. 33 represents a graph of molar absorption coefficients calculatedfrom: the results of absorption spectrum measurement of the dispersionsin which silicon compound-coated cerium oxide particles obtained inExample 3 and cerium oxide particles obtained in Example 8 in which thesurface thereof is uncoated were respectively dispersed in propyleneglycol; and the concentrations of silicon compound-coated cerium oxideparticles in the dispersions used in the measurement. Furthermore, Table19 represents the ratio of silicon compound-coated cerium oxideparticles obtained in each example in Table 19 and the molar absorptioncoefficients of cerium oxide particles obtained in Example 8 atwavelengths of 200 nm to 380 nm in comparison with the molar absorptioncoefficients thereof at wavelengths of 200 nm to 380 nm.

Cerium oxide particles having the same particle diameters as those ofExample 3 were prepared in a manner similar to Example 3 except thatcerium oxide particles obtained in Example 8, which have the surface notcoated with a silicon compound, did not use the third fluid in Example 3and openings d30 of the third introduction portion of the fluidtreatment apparatus and the third introduction portion of the fluidtreatment apparatus described in Patent Literature 6 were not formed.

TABLE 19 Example 3 3-2 3-3 8 M—OH ratio [%] 33.0 30.3 29.1 12.4 Averagemolar absorption 4363 4516 4781 3655 coefficient [L/(mol · cm)] (200-380nm)

As is evident from Table 19, the lower the ratio of M-OH, the higher themolar absorption coefficient tended to be observed. As is evident fromthe table, furthermore, the silicon compound-coated cerium oxideparticles obtained in the example have high molar absorptioncoefficients at wavelengths of 200 nm to 380 nm as compared with thecerium oxide particles obtained in Example 5. In the present invention,preferably, the ratio of M-OH bonds contained in silicon compound-coatedcerium oxide particles is 25% or more and 35% or less, and the siliconcompound-coated cerium oxide particles has a molar absorptioncoefficient of 4000 L/(mol·cm) or more for light rays at wavelengths of200 nm to 380 nm in a dispersion in which the silicon compound-coatedcerium oxide particles are dispersed. As a result, it is possible toefficiently absorb light rays at wavelengths of 200 nm to 380 nm, whichcorrespond to ultraviolet rays of UVA, UVB, and UVC. Thus, such siliconcompound-coated zinc oxide particles can be suitable for attaining afurther increase in transparency while attaining a decrease in theamount used when used for a coating composition.

As described above, the method for producing oxide particles of thepresent invention makes it possible to control delicate and strict colorcharacteristics of silicon compound-coated oxide particles. Thus, whenused in a coating composition, it is possible to strictly controltransmission, absorption, hue, color saturation, and molar absorptioncoefficient for light rays in the ultraviolet, visible, and nearinfrared regions. When applied to the human body, it does not impair thetexture and beauty. When used for a coating body, it can protect thehuman body and painted body from ultraviolet rays and near infrared rayswithout damaging the design.

Example 4

Example 4 describes iron oxide particles. An oxide raw-material liquid(liquid A) and an oxide precipitation solvent (liquid B) were preparedusing a high-speed rotation-type dispersion emulsifier CLERMIX (productname: CLM-2.2S, manufactured by M Technique Co., Ltd.). Specifically,based on the formulation of the oxide raw-material liquid shown inExample 4 of Table 20, the ingredients of the silicon compoundraw-material liquid were homogeneously mixed by stirring them at 20,000rpm for 30 minutes at a preparation temperature of 40° C. using CLEARMIXto prepare a silicon compound raw-material liquid. Furthermore, based onthe formulation of the oxide precipitation solvent shown in Example 4 ofTable 20, the ingredients of the oxide precipitation solvent werehomogeneously mixed by stirring them at a rotor speed of 15,000 rpm for30 minutes at a preparation temperature of 45° C. using CLEARMIX toprepare an oxide precipitation solvent.

Regarding substances indicated by chemical formulas and abbreviationsdescribed in Table 20, NaOH was sodium hydroxide (manufactured byKANTOCHEMICAL CO., LTD.) and Fe(NO₃)₃.9H₂O used was iron nitratenonahydrate (manufactured by KANTOCHEMICAL CO., LTD.).

Subsequently, the prepared oxide raw-material liquid and the oxideprecipitation solvent were mixed together using a fluid treatmentapparatus described in Patent Literature 6 of the present applicant. Amethod for treating each fluid and a method for collecting the treatedliquid were carried out in a manner similar to Example 1. In addition,Example 4 did not use the third introduction portion d3 and liquid C(not shown).

As in the case with Example 1, Table 21 represents the operatingconditions of the fluid treatment apparatus and the average primaryparticle diameter calculated from the results of the TEM observation ofthe resulting iron oxide particles. The procedures for pH measurement,analysis, and particle-washing were also carried out in the same manneras in Example 1. As a result of the TEM observation, the primaryparticle diameters were approximately 5 nm to 15 nm, and as described inTable 21, the average primary particle diameter was 9.53 nm.

TABLE 20 Example 4 Formulation of the 1st fluid Formulation of the 2ndfluid (liquid A: Oxide raw material liquid) (liquid B: Oxideprecipitation solvent) Formulation Formulation Raw Raw pH Raw Raw pHmaterial [wt %] material [wt %] pH [° C.] material [wt %] material [wt%] pH [° C.] Fe(NO₃)₃ 2.00 Pure 98.00 1.8 26.6 NaOH 9.00 Pure 91.00 >14— 9H₂O water water

TABLE 21 Example 4 Introduction flow Introduction Introduction ratetemperature pressure (liquid feed flow (liquid feed (liquid feed Averagerate) temperature) pressure) Discharged primary [ml/min] [° C.] [MPaG]liquid particle Liquid Liquid Liquid Liquid Liquid Liquid Temp. diameterA B A B A B pH [° C.] [nm] 400 40 142 86 0.436 0.10 11.59 29.9 9.53

The iron oxide particles obtained in Example 4 were subjected to a heattreatment using an electric furnace to modify the functional groupscontained in the iron oxide particles. The heat treatment conditionswere as follows: untreated in Example 4; 100° C. in Example 4-2; 200° C.in Example 4-3; and 300° C. in Example 4-4. For each heat treatmenttemperature, the duration of heat treatment was 30 minutes. The ironoxide particles obtained in Example 4-2 to Example 4-4 also had primaryparticle diameters of approximately 5 nm to 15 nm.

FIG. 35 represents the results of XRD measurement of iron oxideparticles obtained in Example 4. As is evident from FIG. 35, only thepeaks that came from iron oxide (α-Fe₂O₃) were detected in the XRDmeasurement. Similarly, for the results of XRD measurements in Example4-2 to 4-4, peaks derived from iron oxide were only detected asillustrated in FIG. 35.

FIG. 36 represents the results of FT-IR measurement of the iron oxideparticles obtained in Example 4 and Example 4-4 by the ATR method. Fromthe IR measurement results of the iron oxide particles obtained inExample 4-4, as compared with the results of IR measurement on the ironoxide obtained in Example 4, broad peaks in the vicinity of 800 cm⁻¹ to1250 cm⁻¹ originated from the M-OH bonds and peaks in the vicinity of1250 cm⁻¹ to 1750 cm⁻¹, which can be caused by reaction of M-OH bondswith carbon oxide, can be recognized smaller.

The results obtained by waveform separation peaks at wavenumbers of 100cm⁻¹ to 1250 cm⁻¹ in the IR measurement are represented in FIG. 37 forExample 4 and FIG. 38 for Example 4-4. In Example 4-4, since the peakwaveform-separated to the M-OH bond is very small, it is shown togetherwith the enlarged view of the region at wavelengths of 800 cm⁻¹ to 1250cm⁻¹. Compared with Example 4, with respect to the total area of peaksof M-OH bonds, the iron oxide particles obtained in Example 4-4 aresmaller than the total area of all waveform-separated peaks, or smallerratio of M-OH bonds.

FIG. 39 is a graph of the molar absorption coefficients of dispersionsin which zinc oxide particles obtained in Example 4-4 to Example 4 andExample 4-2 were respectively dispersed in propylene glycol atwavelengths of 190 nm to 780 nm. Table 22 represents the molarabsorption coefficient for light rays at wavelengths of 190 nm to 380nm. FIG. 40 represents a graph of the molar absorption coefficient forlight rays at wavelengths of 190 nm to 380 nm with respect to the ratioof M-OH of the iron oxide particles obtained in Example 4 and Example4-2 to Example 4-2. As is evident from FIG. 39 and Table 22, the molarabsorption coefficient for light rays at wavelengths of 190 nm to 380 nmwere improved as the M-OH ratio decreased in the order of Examples 4,4-2, 4-3, and 4-4.

TABLE 22 Example 4 4-2 4-3 4-4 M—OH ratio [%] 7.8 7.3 4.1 1.8 Averagemolar absorption 770 1477 1995 2048 coefficient [L/(mol · cm)] (190-380nm)

Further, as is evident from FIG. 40, unlike the silicon compound-coatediron oxide particles obtained in Example 1, an M-OH ratio of 1.5% ormore and 7.5% or less in iron oxide particles can attain a molarabsorption coefficient of 1000 L/(mol·cm) or more for light rays atwavelengths of 190 nm to 380 nm.

FIG. 41 represents the measurement results of the reflection spectrum ofthe iron oxide particles obtained in each of Example 4 and Examples 4-2to 4-4 for light rays at wavelengths of 200 nm to 2500 nm. FIG. 42represents a graph of the average reflectance of the oxide particles forlight rays at wavelengths of 780 nm to 2500 nm in the near-infraredregion with respect to the ratio of M-OH calculated from the IR spectrumof each example.

Table 23 represents the average reflectance of the oxide particles forlight rays at wavelengths of 780 nm to 2500 nm of the iron oxideparticles obtained in Example 4 and Examples 4-2 to 4-4.

TABLE 23 Example 4 4-2 4-3 4-4 M—OH ratio [%] 7.8 7.3 4.1 1.8 Averagereflectance [%] 54.4 59.2 66.4 70.7 (780-2500 nm)

As is evident from Table 23 and FIG. 42, the lower the ratio of M-OH,the higher the average reflectance for light rays at wavelengths of 780nm to 2500 nm tended to be observed. When the ratio of M-OH bondcontained in the iron oxide particles was in the range of 1.5% or moreand 7.5% or less, the average reflectance value for rays in thenear-infrared range at wavelengths of 780 nm to 2500 nm was more than55%.

Example 4-5 to Example 4-7

Subsequently, iron oxide particles were prepared in a manner similar toExample 4 except that, in Example 4, the dispersion of iron oxideparticles were discharged from the fluid treatment apparatus, collectedin the beaker, and subjected to the dispersion modifier 100 shown inFIG. 34. Table 24 represents conditions for controlling the ratio ofM-OH bonds in the iron oxide particle using the dispersion modifier 100in FIG. 34. Iron oxide particles with the controlled ratio of M-OH bondswere prepared in a manner similar to Example 1-11 to Example 1-13,excepting of the contents of Table 24.

Both the procedures for dispersing the dispersion of iron oxideparticles and procedures for removal of impurities in the dispersion ofiron oxide particles were carried out repeatedly until the pH of thedispersion of iron oxide particles reached 7.34 (measurementtemperature: 23.6° C.) and the conductivity thereof reached 6.99 μS/cm.The impurities contained in the aggregates of silicon compound-coatediron oxide particles were also removed. Thus, each of the iron oxideparticles in the dispersion thereof was modified.

TABLE 24 Examples 4-5 Processing solution Iron oxide particle dispersionliquid  (1) 1st amount of solution charged into container Type: Purewater 130 pH 5.89 (measurement temperature: 22.4° C.) Conductivity 0.80μS/cm (measurement temperature 22.4° C.) Input: 15 kg  (2) Type, flowrate, and temperature of cross flow Type: Pure water cleaning liquid pH5.89 (measurement temperature: 22.4° C.) Conductivity 0.80 μS/cm(measurement temperature 22.4° C.) Flow rate: 1.5 L/min, 21° C.  (3)Dispersing machine 102 CLEARMIX (product name: CLM-2. 2S, rotor: R1,screen: S 0.8-48, manufactured by M Technique Co., Ltd.)  (4) Removalpart 120 Hollow fiber type dialyzer PN-220 (film area: 2.2 m², material:polysulfone), manufactured by Nikkiso Co., Ltd.  (5) Rotor speed 20,000rpm (peripheral speed: 31.4 m/S)  (6) Start of charging oxide particledispersion When the first pure water inside the vessel 130 has beenreduced to 1 L  (7) Input of oxide particle dispersion into oxide 14 L(ca. 14 kg) container 130  (8) pH of oxide particle dispersion liquidinside 11.23 (measuring temperature: 25.9° C.) vessel 130  (9)Conductivity of oxide particle dispersion liquid 6999 μS/cm (measurementtemperature: 25.8° C.) inside the vessel 130 (10) Flow rate of pump 1048.8 L/min (11) Flow rate oxide particle dispersion liquid is 7.3 L/minreturned to storage container 130 (12) Discharge amount (calculatedvalue) of filtrate 1.5 L/min L3 by removal part 120 (13) Timing ofintroduction of diluent into container When the dispersion amount instorage container 130 is 130 concentrated to 1.5 L (14) Type and inputof 2nd different dilution to Type: Pure water storage container 130 pH5.89 (measurement temperature: 22.4° C.) Conductivity 0.80 μS/cm(measurement temperature 22.4° C.) Input: 13.5 L (ca. 13.5 kg) (15)Concentration of oxide particles in oxide 0.4 wt % to 2.0 wt % particledispersion (16) Pressure gauge Pa: Both of two are 0.10 MPaG (17)Pressure gauge Pb: 0.15 MPaG (18) Pressure gauge Pc 0.02 MPaG (19) Pathlength (Lea)   0.3 m (20) Pipping inner diameter (Leb) 0.0105 m (21)Flow velocity of oxide particle dispersion liquid 1.2 m/sec inimmediately preceding transport path (22) Time T1 until removal part 120starts removal 0.24 sec of impurities from dispersion container 101 (23)Thermometer placed in the dispersion 23° C. to 26° C. container 101 (24)Temperature of oxide particle dispersion 23° C. to 26° C. (25)Conductivity measuring machine Electrical conductivity meter, modelnumber ES-51 manufactured by HORIBA, Ltd.

By changing the treatment temperature in the modification of thedispersion of iron oxide particles shown in (23) and (24) of Table 24,iron oxide particles having different ratios of M-OH in Examples 4-5 to4-7 were prepared. Table 25 represents, together with the results ofExample 4, the treatment temperature for modifying the dispersion ofiron oxide particles, the ratio of M-OH in the resulting iron oxideparticles, the average reflectance at wavelengths of 780 nm to 2500 nm,the average reflectance at wavelengths of 380 nm to 780 nm, the averagetransmittance thereof at wavelengths 380 nm to 780 nm, and the molarabsorption coefficient at wavelengths of 190 nm to 380 nm.

TABLE 25 Example 4 4-5 4-6 4-7 Treatment temperature — 23-26 43-46 59-61(Table 24: (23)) [° C.] Treatment temperature — 23-26 43-46 59-61 (Table24: (24)) [° C.] M—OH ratio [%] 7.8 7.2 6.2 5.3 Average reflectance [%]54.4 58.6 62.1 64.1 (780-2500 nm) Average molar absorption 770 1468 15981798 coefficient [L/(mol · cm)] (190-380 nm)

As is evident from FIG. 25, the lower the ratio of M-OH, the higher theaverage reflectance values thereof at wavelengths of 780 nm to 2500 nmand the molar absorption coefficients thereof at wavelengths of 190 nmto 380 nm tended to be observed. Thus, it is found that the colorcharacteristics of the oxide particles can be controlled by controllingthe ratio of M-OH.

Example 4-8

Iron oxide particles were prepared as those of Example 4-8 in a mannersimilar to Example 4 except that the apparatus described in JP2009-112892 and procedures for mixing and reacting liquid A (oxideraw-material liquid) with liquid B (oxide precipitation solvent) wereemployed. Here, the apparatus described in JP 2009-112892 is onedescribed in FIG. 1 of this publication. The inner diameter of astirring tank was 80 mm, the gap between the outer end of a stirringtool and the inner peripheral side surface of the stirring tank was 0.5mm, and the rotational speed of the stirring blade was 7.200 rpm. Inaddition, liquid A was introduced into the stirring tank, and liquid Bwas then added to a thin film composed of liquid A being pressed againstthe inner peripheral side surface of the stirring tank to mix and reactwith each other. As a result of TEM observation, iron oxide particles ofapproximately 50 nm to 60 nm in primary particle diameter were observed.

The iron oxide particles obtained in Example 4-8 were subjected to aheat treatment using an electric furnace to modify the functional groupscontained in the iron oxide particles. The heat treatment conditionswere as follows: untreated in Example 4-8; 100° C. in Example 4-9; 200°C. in Example 4-10; and 300° C. in Example 4-11. For each heat treatmenttemperature, the duration of heat treatment was 30 minutes. Table 26represents the average primary particle diameter and the ratio of M-OHof the iron oxide particles obtained in Examples 4-8 to 4-11, as well asthe average reflectance values thereof at wavelengths of 780 nm to 2500nm and the molar absorption coefficient thereof at wavelengths of 190 nmto 380 nm. The molar absorption coefficient of the iron oxide particlesprepared in Examples 4-8 to 4-11 was measured using propylene glycol asa dispersion medium in the same manner as in Example 4.

TABLE 26 Example 4-8 4-9 4-10 4-11 Average primary particle 55.9 55.455.6 55.7 diameter [nm] M—OH ratio [%] 8.2 7.4 3.8 1.6 Averagereflectance [%] 53.1 59.1 63.1 69.2 (780-2500 nm) Average molarabsorption 695 1402 1649 1888 coefficient [L/(mol · cm)] (190-380 nm)

As is evident in Table 26, even in the case of using zinc oxideparticles produced by using an apparatus different from those ofExamples 1 to 4, the functional groups contained in the zinc oxideparticles having primary particle diameters of 100 nm or less can bemodified to control the molar absorption coefficient thereof atwavelengths of 190 nm to 380 nm and the average reflectance valuesthereof at wavelengths of 780 nm to 2500 nm.

Comparative Example 1

Iron oxide particles (special grade iron oxide (III) (α-Fe₂O₃)manufactured by Wako Pure Chemical Industries, Ltd.) having primaryparticle diameters of 150 nm to 250 nm were subjected to a heattreatment in an electric furnace to modify the functional groupscontained in the iron oxide particles for changing the ratio of M-OHbonds. The heat treatment conditions were as follows: untreated inComparative Example 1-1; 100° C. in Comparative Example 1-2; and 300° C.in Comparative Example 1-3. For each heat treatment temperature, theduration of heat treatment was 30 minutes. For iron oxide particles ofComparative Examples 1-1 to 1-3, Table 27 represents the ratio of M-OHand the molar absorption coefficient for light rays at wavelengths of190 nm to 380 nm in a dispersion in which the iron oxide particles weredispersed in a manner similar to Example 4. As is evident from Table 27,in the case of iron oxide particles having primary particle diameters ofmore than 100 nm or more, even when the ratio of M-OH bonds was changed,the molar absorption coefficient was low, resulting in no observedincreasing tendency. In comparison between Comparative Example 1-1 andExample 4-4 in particular, even the iron oxide particles have the ratioof M-OH similar to the iron oxide particles having primary particlediameters of 50 nm or less obtained in Example 4-4, it is found that theiron oxide particles of Comparative Example 1-1 have lower molarabsorption coefficients in a region at wavelengths of 190 nm to 380 nm.In the present invention, when the primary particle diameter is as smallas 50 nm or less, the ratio of M-OH affects the color characteristics.That is, in a state where the surface area is increased with respect tothe same amount of iron oxide particles, color characteristics can becontrolled by controlling the M-OH ratio.

TABLE 27 Comparative Example 1-1 1-2 1-3 M—OH ratio [%] 1.7 1.6 1.5Average molar absorption 331 333 329 coefficient [L/(mol · cm)] (190-380nm)

Example 5

Example 5 describes zinc oxide particles. Using a high-speedrotation-type dispersion emulsifier CLEARMIX (product name: CLM-2.2S,manufactured by M Technique Co., Ltd.), an oxide raw-material liquid andan oxide precipitation solvent were prepared. Specifically, based on theformulation of the oxide raw-material liquid shown in Example 5 of Table28, using CLEARMIX at a rotor rotational speed of 20,000 rpm, therespective ingredients of the zinc oxide raw-material liquid werestirred and homogeneously mixed together at a preparation temperature of40° C. for 30 minutes to prepare an oxide raw-material liquid.Furthermore, based on the formulation of the oxide precipitation solventshown in Example 5 of Table 28, using CLEARMIX at a rotor rotationalspeed of 15,000 rpm, the respective ingredients of the oxideprecipitation solvent were stirred and homogeneously mixed together at apreparation temperature of 45° C. for 30 minutes to prepare an oxideprecipitation solvent. Regarding substances indicated by chemicalformulas and abbreviations described in Table 28, 97 wt % H₂SO₄ used wasconcentrated sulfuric acid (manufactured by Kishida Chemical Co., Ltd.),KOH used was potassium hydroxide (manufactured by manufactured by NipponSoda Co., Ltd.), and ZnO used was zinc oxide (manufactured byKANTOCHEMICAL CO., LTD.).

Subsequently, the prepared oxide raw-material liquid and oxideprecipitation solvent were mixed together using a fluid treatmentapparatus described in Patent Literature 6 of the present applicant. Amethod for treating each fluid and a method for collecting the treatedliquid were carried out in a manner similar to Example 1. In Example 5,furthermore, third foreword d3 and liquid C were not used (not shown).

Similar to Example 1, Table 29 represents the operating conditions ofthe fluid treatment apparatus and the average primary particle diameterof the resulting zinc oxide particles calculated from the results of TEMobservation. The procedures for pH measurement, analysis, andparticle-washing were also carried out in the same manner as in Example2.

(Haze Value Measurement)

In the evaluation of Example 5, the haze value of a dispersion of zincoxide particles was also measured. A haze level meter (model HZ-V3,manufactured by Suga Test Instruments Co., Ltd.) was used for haze levelmeasurement. As the optical condition, D65 light was used as a lightsource by a double beam method corresponding to JIS K 7136 or JIS K7361. The measurement was performed on the same dispersion as one usedfor the transmission spectrum measurement in a liquid cell of 1 mm inthickness.

TABLE 28 Example 5 Formulation of the 1st fluid Formulation of the 2ndfluid (liquid A: Oxide precipitation solvent) (liquid B: Oxide rawmaterial liquid) Formulation Formulation Raw Raw pH Raw Raw Raw pHmaterial [wt %] material [wt %] pH [° C.] material [wt %] material [wt%] material [wt %] pH [° C.] MeOH 93.71 97 wt % 6.29 <1 — ZnO 3.00 KOH46.56 Pure 50.44 >14 — H₂SO₄ water

TABLE 29 Example 5 Introduction flow Introduction Introduction ratetemperature pressure (liquid feed flow (liquid feed (liquid feed Averagerate) temperature) pressure) Discharged primary [ml/min] [° C.] [MPaG]liquid particle Liquid Liquid Liquid Liquid Liquid Liquid Temp. diameterA B A B A B pH [° C.] [nm] 575 50 28 28 0.106 0.112 13.66 24.1 9.4

FIG. 43 represents a TEM photograph of zinc oxide particles obtained inExample 5. The zinc oxide particles obtained in Example 5 had primaryparticle diameters of approximately 5 nm to 15 nm and an average primaryparticle diameter of 9.4 nm as described in Table 29.

Hydrogen peroxide was acted on the zinc oxide particles obtained inExample 5 to modify the functional groups contained in the zinc oxideparticles. Specifically, one part by weight of the zinc oxide particlesobtained in Example 5 was charged into 99 parts by weight of propyleneglycol (manufactured by Kishida Chemical Co., Ltd.), and subjected toI-hour dispersion treatment using a high-speed rotation-type dispersionemulsifier CLEARMIX (product name: CLM-2.2S, manufactured by M TechniqueCo., Ltd) at a rotor speed of 20,000 rpm at 25° C. to prepare adispersion. Hydrogen peroxide water (manufactured by KANTO CHEMICAL CO.,LTD. Purity: 30.9%) was added to the propylene glycol dispersion of thezinc oxide particles and the mixture was then stirred at 25° C. for 15minutes using the high-speed rotation-type dispersion emulsifier. Theresulting treated liquid was centrifuged at 26,000 G for 15 minutes, andthe supernatant was then removed to obtain a precipitate. A part of theprecipitate was dried at −0.10 MPaG at 25° C. for 20 hours to obtain adried powder.

The amount of the hydrogen peroxide liquid was changed, and thetreatment was then carried out by changing the molar ratio of hydrogenperoxide to zinc oxide particles. The molar ratio of hydrogen peroxideto zinc oxide particles (H₂O₂/ZnO [molar ratio]) is ×0.01 mol forExample 5-2, ×0.50 for Example 5-3, and ×1.00 for Example 5-4. FIG. 44represents a TEM photograph of zinc oxide particles obtained in Example5-4. The zinc oxide particles obtained in Example 5-4 also had primaryparticle diameters of approximately 5 nm to 15 nm and an average primaryparticle diameter of 9.5 nm.

FIG. 45 is a diagram illustrating the results of XRD measurement of zincoxide particles obtained in Example 5 of the present invention. As canbe found in FIG. 45, only the peaks that came from zinc oxide (ZnO) weredetected in the XRD measurement. Similarly, for the results of XRDmeasurements in Example 5-2 to 5-4, peaks derived from iron oxide wereonly detected as illustrated in 45.

FIG. 46 represents the results of FT-IR measurement of the zinc oxideparticles obtained in Example 5 and Example 5-4 by the ATR method. Fromthe IR measurement results of the iron oxide particles obtained inExample 5-4, as compared with the results of IR measurement on the ironoxide obtained in Example 5, broad peaks in the vicinity of 750 cm⁻¹ to1250 cm⁻¹ originated from the M-OH bonds and peaks in the vicinity of1300 cm⁻¹ to 1500 cm⁻¹, which might be caused by reaction of M-OH bondswith carbon oxide, are recognized smaller.

The results obtained by waveform separation peaks at wavenumbers of 100cm⁻¹ to 1250 cm⁻¹ in the IR measurement are represented in FIG. 47 forExample 5, FIG. 48 for Example 5-2, and FIG. 49 for Example 5-4. Withrespect to peaks waveform-separated to M-OH bonds, in Examples 5-2 and5-4, no waveform-separated peak (M-OH bond 2) was confirmed in thevicinity of 1100 cm⁻¹. Thus, the peak fitted to the waveform (M-OH bond2) in the vicinity of 1100 cm⁻¹ became smaller to cause a decrease inthe ratio of M-OH bonds. Table 30 represents the molar ratio of hydrogenperoxide to zinc oxide particles (H₂O₂/ZnO [molar ratio]), the averageprimary particle diameter of the resulting zinc oxide particles, and theratio of M-OH. As is evident from Table 30, the ratio of M-OH can becontrolled by treating zinc oxide particles with hydrogen peroxide.

FIG. 50 is a graph of the molar absorption coefficients of dispersionsin which zinc oxide particles obtained in Example 5 and Example 5-2 toExample 5-4 were respectively dispersed in propylene glycol atwavelengths of 200 nm to 780 nm. Table 30 represents the molarabsorption coefficients for light rays at wavelengths of 200 nm to 380nm. As is evident from FIG. 50 and Table 30, the molar absorptioncoefficients thereof at wavelengths of 200 nm to 380 nm can becontrolled by controlling the ratio of M-OH.

FIG. 51 represents the reflectance spectra of the zinc oxide particlesobtained in Example 5 and Examples 5-2 to 5-4, and Table 30 representsthe average reflectance values thereof at wavelengths of 780 nm to 2500nm. As is evident from FIG. 51 and Table 30, the average reflectancevalues thereof at wavelengths of 780 nm to 2500 nm can be controlled bycontrolling the ratio of M-OH.

FIG. 52 represents transmission spectra of dispersions in which zincoxide particles obtained in Examples 5 and Example 5-2 to 5-4 wererespectively dispersed in propylene glycol as ZnO at a concentration of0.011% by weight in propylene glycol. It is recognized that the lowerthe ratio of M-OH, the higher the average reflectance for light rays atwavelengths of 200 nm to 360 nm tended to be shifted to the longwavelength side. It is found that, by controlling the ratio of M-OH,zinc oxide particles suitable for use in a coating composition intendedfor ultraviolet shielding can be produced. Table 30 represents thetransmittance for light rays at wavelengths of 330 nm, thetransmittances for light rays at wavelengths 380 nm to 780 nm, and hazevalues. For all of Example 5 and Example 5-2 to Example 5-4, thetransmittance for light rays at a wavelength of 330 nm was 10% or less,the transmittances for light rays at wavelengths 380 nm to 780 nm were90% or more, and the haze value is 1% or less.

TABLE 30 Example 5 5-2 5-3 5-4 Average primary particle 9.4 9.5 9.5 9.6diameter [nm] H₂O₂/ZnO [molar ratio] 0.00 0.01 0.50 1.00 M—OH ratio [%]11.8 9.0 8.3 8.2 Average molar absorption 623 723 739 744 coefficient[L/(mol · cm)] (200-380 nm) Average reflectance [%] 68.3 72.4 74.8 75.3(780-2500 nm) Transmittance [%] 7.0 7.5 7.4 7.4 (330 nm) Averagetransmittance [%] 96.4 96.5 97.0 96.9 (380-780 nm) Haze value [%] 0.020.02 0.04 0.02

The zinc oxide particles obtained in Example 5 were heat-treated usingan electric furnace to modify the functional groups contained in thezinc oxide particles. The heat treatment conditions were as follows:untreated in Example 5; 100° C. in Example 5-5; 200° C. in Example 5-6;and 300° C. in Comparative Example 5-7. For each heat treatmenttemperature, the duration of heat treatment was 30 minutes. FIG. 53represents a TEM photograph of zinc oxide particles obtained in Example5-6. The zinc oxide particles obtained in Example 5-6 had primaryparticle diameters of approximately 5 nm to 20 nm and an average primaryparticle diameter of 10.4 nm. Also, the zinc oxide particles obtained inExample 5-5 had an average primary particle diameter of 9.5 nm andExample 5-7 an average primary particle diameter of 9.6 nm.

FIG. 54 represents the results of FT-IR measurement of the zinc oxideparticles obtained in Example 5 and Example 5-6 by the ATR method.Compared to the zinc oxide particles of Example 5, it can be seen thatthe zinc oxide particles obtained in Example 5-6 have smaller peaks atwavelengths of 800 cm⁻¹ to 1250 cm⁻¹, which are the peaks of M-OH bonds,or the ratio of M-OH bonds is smaller.

FIG. 55 is a graph of the molar absorption coefficients of dispersionsin which zinc oxide particles obtained in Example 5 and Example 5-5 toExample 5-7 and zinc oxide particles having primary particle diametersof more than 50 nm obtained in Comparative Example 2-1, which will bedescribed later, were respectively dispersed in propylene glycol atwavelengths of 200 nm to 380 nm. As is evident from FIG. 55 and Table31, the molar absorption coefficient for light rays at wavelengths of200 nm to 380 nm were improved as the M-OH ratio decreases in the orderof Examples 5, 5-5, 5-6, and 5-7.

TABLE 31 Example 5 5-5 5-6 5-7 M—OH ratio [%] 11.8 8.7 5.3 1.4 Averagemolar absorption 623 726 902 965 coefficient [L/(mol · cm)] (200-380 nm)

As is evident from Table 31 and FIG. 55, as the ratio of M-OH bonds(M-OH ratio) of zinc oxide particles became smaller in the range of 12%or less, the molar absorption coefficient for light rays at wavelengthsof 200 nm to 380 nm became larger. In the present invention, preferablezinc oxide particles are those in which the ratio of M-OH bondscontained therein is 12% or less and the molar absorption coefficientthereof is 500 L/(cm·mol) or more at wavelengths of 200 nm to 380 nm.More preferable zinc oxide particles are those in which the ratio ofM-OH bonds contained therein is 11.2% or less and the molar absorptioncoefficient thereof is 650 L/(cm·mol) or more at wavelengths of 200 nmto 380 nm.

FIG. 56 represents the reflectance spectra of the zinc oxide particlesobtained in Example 5 and Examples 5-5 to 5-7 for light rays atwavelengths of 200 nm to 2500 nm. FIG. 57 represents a graph of theaverage reflectance for light rays at wavelengths of 780 nm to 2500 nmin the near-infrared region with respect to the ratio of M-OH calculatedfrom the IR spectrum of each example.

FIG. 58 is a diagram illustrating the results of reflection spectrummeasurement of zinc oxide particles for light rays at wavelengths of 200nm to 780 nm, the oxide particles being obtained in each of Example 5and Examples 5-5 to 5-7. As is evident from FIG. 58, it is recognizedthat the lower the ratio of M-OH, the higher the average reflectance forlight rays at wavelengths of 200 nm to 360 nm tended to be shifted tothe long wavelength side. Table 32 represents: the average reflectanceof the zinc oxide particles obtained in Example 5 and Example 5-5 toExample 5-7 for light rays at wavelengths of 780 nm to 2500 nm; thetransmittance in a transmission spectrum at wavelengths of 330 nm of thedispersion in which the zinc oxide particles obtained in each of theseexamples were dispersed as ZnO of 0.011 wt %; an average transmittancefor light rays at wavelengths of 380 nm to 780 nm; and haze value.

TABLE 32 Example 5 5-5 5-6 5-7 M—OH ratio [%] 11.8 8.7 5.3 1.4 Averagereflectance [%] 68.3 74.1 79.8 82.7 (780-2500 nm) Transmittance [%] 7.07.5 6.9 7.4 (330 nm) Average transmittance [%] 96.4 97.0 96.5 96.5(380-780 nm) Haze value [%] 0.02 0.02 0.03 0.04

As is evident from FIGS. 56 and 57 and Table 32, the lower the ratio ofM-OH, the higher the average reflectance for light rays at wavelengthsof 780 nm to 2500 nm tended to be observed. In the zinc oxide particlesobtained in Example 5 and Examples 5-5 to Example 5-7, the averagereflectance value for rays in the near infrared region at wavelengths of780 nm to 2500 nm was 65% or more. Further, although the transmittanceof the zinc oxide particle dispersion was 10% or less for the light raysat a wavelength of 330 nm, the average transmittance of the zinc oxideparticle dispersion for the light ray at wavelengths of 380 nm to 780 nmwas 90% or more. In addition, the haze value was a very low value in therange of 0.02% to 0.04%.

Comparative Example 2

The ratio of M-OH bonds was changed for zinc oxide particles havingprimary particle diameters of 150 nm to 300 nm (manufactured by KANTOCHEMICAL CO., LTD. Special grade 3N5). FIG. 59 represents a TEMphotograph of Comparative Example 1. The zinc oxide particles wereheat-treated using an electric furnace to modify the functional groupscontained in the zinc oxide particles. The heat treatment conditionswere as follows: untreated in Comparative Example 2-1; 100° C. inComparative Example 2-2: and 300° C. in Comparative Example 2-3. Foreach heat treatment temperature, the duration of heat treatment was 30minutes. Table 33 represents: the M-OH ratio of the zinc oxide particlesobtained in each of Comparative Example 2-1 to Comparative Example 2-3:the molar absorption for light rays at wavelengths of 200 nm to 380 nmin the dispersion obtained by dispersing the zinc oxide particles inpropylene glycol; the transmittance in a transmission spectrum atwavelengths of 330 nm of the dispersion in which the zinc oxideparticles obtained in each of these examples were dispersed as ZnO of0.11 wt %; an average transmittance for light rays at wavelengths of 380nm to 780 nm; and haze value. As is evident from Table 33, zinc oxideparticles having primary particle diameters of more than 50 nm showedsubstantially no difference in the aforementioned molar absorptioncoefficient, transmittance, and haze value even when the ratio of M-OHbonds was changed, thereby having low ultraviolet absorption capacityand low transparency. In comparison between Comparative Example 2-1 andExample 5-7 in particular, even the zinc oxide particles have the ratioof M-OH similar to the zinc oxide particles having primary particlediameters of 50 nm or less obtained in Example 5-7, it is found that thezinc oxide particles of Comparative Example 2-1 have lower molarabsorption coefficients in a region at wavelengths of 200 nm to 380 nm.In the present invention, when the primary particle diameter is as smallas 50 nm or less, the ratio of M-OH affects the color characteristics.That is, in a state where the surface area is increased with respect tothe same amount of zinc oxide particles, color characteristics can becontrolled by controlling the M-OH ratio. Furthermore, the averageprimary particle diameter of Comparative Example 2-1 was 228 nm, theaverage primary particle diameter of Comparative Example 2-2 was 228 nm,and the average primary particle diameter of Comparative Example 2-3 was225 nm.

TABLE 33 Comparative Example 2-1 2-2 2-3 M—OH ratio [%] 1.6 0.8 0.2Average molar absorption 196 197 199 coefficient [L/(mol · cm)] (200-380nm) Transmittance [%] 15.1 15.6 15.3 (330 nm) Average transmittance [%]65.1 66.4 66.5 (380-780 nm) Haze value [%] 3.68 3.81 3.78

Comparative Example 3

The zinc oxide particles obtained in Example 5 were heat-treated usingan electric furnace to modify the functional groups contained in thezinc oxide particles. The heat treatment conditions were 400° C.(Comparative Example 3-1) and 600° C. (Comparative Example 3-2). Foreach heat treatment temperature, the duration of heat treatment was 30minutes. The TEM photographs of zinc oxide particles treated under theseheat-treatment conditions are shown in FIG. 60 (Comparative Example 3-1)and FIG. 61 (Comparative Example 3-2), respectively. As illustrated inFIG. 60 and FIG. 61, obvious fusion bonding of the zinc oxide particleswas observed, and the primary particle diameters of some of themexceeded 50 nm. Table 34 represents: the M-OH ratio of the zinc oxideparticles obtained in each of Comparative Example 3-1 and ComparativeExample 3-2; the molar absorption for light rays at wavelengths of 200nm to 380 nm in the dispersion obtained by dispersing the zinc oxideparticles in propylene glycol; the transmittance in a transmissionspectrum at wavelengths of 330 nm of the dispersion in which the zincoxide particles obtained in each of these examples were dispersed as ZnOof 0.11 wt %; an average transmittance for light rays at wavelengths of380 nm to 780 nm; and haze value.

TABLE 34 Comparative Example 3-1 3-2 M-OH ratio [%] 0.6 0.2 Averagemolar absorption 239 237 coefficient [L/(mol · cm)] (200-380 nm)Transmittance [%] 13.2 13.1 (330 nm) Average transmittance [%] 66.4 64.9(380-780 nm) Haze value [%] 2.35 2.39

As is evident from Table 34, as in Comparative Example 1, zinc oxideparticles having primary particle diameters of more than 50 nm showedsubstantially no difference in the aforementioned molar absorptioncoefficient, transmittance, and haze value even when the ratio of M-OHbonds was changed, thereby having low ultraviolet absorption capacityand low transparency.

Example 6

zinc oxide particles were prepared as those of Example 6-1 in a mannersimilar to Example 5 except that the apparatus described in JP2009-112892 and procedures for mixing and reacting liquid A (oxideraw-material liquid) with liquid B (oxide precipitation solvent) wereemployed. Here, the apparatus described in JP 2009-112892 is onedescribed in FIG. 1 of this publication. The inner diameter of astirring tank was 80 mm, the gap between the outer end of a stirringtool and the inner peripheral side surface of the stirring tank was 0.5mm, and the rotational speed of the stirring blade was 7,200 rpm. Inaddition, liquid A was introduced into the stirring tank, and liquid Bwas then added to a thin film composed of liquid A being pressed againstthe inner peripheral side surface of the stirring tank to mix and reactwith each other. As a result of TEM observation, zinc oxide particles ofapproximately 30 nm in primary particle diameter were observed.

The zinc oxide particles obtained in Example 6-1 were subjected to aheat treatment using an electric furnace to modify the functional groupscontained in the zinc oxide particles. The heat treatment conditionswere as follows: untreated in Example 6-1; 100° C. in Example 6-2; 200°C. in Example 6-3; and 300° C. in Example 6-4. For each heat treatmenttemperature, the duration of heat treatment was 30 minutes. Table 35represents, of the zinc oxide particles obtained in Example 6-1 toExample 6-4, the M-OH ratio, the average molar absorption coefficient atwavelengths of 200 nm to 380 nm, the average reflectance for light raysat wavelengths of 780 nm to 2500 nm, the transmittance for light rays ata wavelength of 330 nm, the average transmittance at wavelengths of 380nm to 780 nm, and haze value. In addition, the transmittances and molarabsorption coefficients of zinc oxide particles respectively prepared inExample 6-1 to Example 6-4 were measured using propylene glycol as adispersion medium in a manner similar to Example 5.

TABLE 35 Example 6-1 6-2 6-3 6-4 Average primary particle 35.6 36.4 35.835.9 diameter [nm] M-OH ratio [%] 11.2 9.2 4.8 1.0 Average molarabsorption 651 718 909 972 coefficient [L/(mol · cm)] (200-380 nm)Average reflectance [%] 69.4 71.9 80.2 83.2 (780-2500 nm) Transmittance[%] 8.6 8.8 9.1 9.2 (330 nm) Average transmittance [%] 92.1 93.1 92.493.3 (380-780 nm) Haze value [%] 0.29 0.31 0.35 0.39

As is evident in Table 35, even in the case of using zinc oxideparticles produced by using an apparatus different from those ofExamples 1 to 5, the ratio of M-OH can be controlled by modifying thefunctional groups contained in the zinc oxide particles having primaryparticle diameters of 50 nm or less to control the molar absorptioncoefficient thereof at wavelengths of 200 nm to 380 nm and the averagereflectance values thereof at wavelengths of 780 nm to 2500 nm. For allof Example 6-1 to Example 6-4, the transmittance for light rays at awavelength of 330 nm was 10% or less, the transmittances for light raysat wavelengths 380 nm to 780 nm were 90% or more, and the haze value is1% or less.

Comparative Example 4

As Comparative Example 4-1, zinc oxide particles were prepared in amanner similar to Example 6-1 except that the distance between the gapbetween the outer end of the stirring tool and the inner peripheral sidesurface of the stirring tank was 1 mm, and the rotational speed of thestirring blade was one sixth (1,200 rpm) of the rotary speed employed inExample 6. As a result of TEM observation, zinc oxide particles ofapproximately 70 nm in primary particle diameter were observed.

The iron oxide particles obtained in Comparative Example 4-1 weresubjected to a heat treatment using an electric furnace to modify thefunctional groups contained in the iron oxide particles. The heattreatment conditions were as follows: untreated in Comparative Example4-1; 100° C. in Comparative Example 4-2; and 300° C. in ComparativeExample 4-3. For each heat treatment temperature, the duration of heattreatment was 30 minutes. Table 36 represents, of the zinc oxideparticles obtained in Comparative Example 4-I to Comparative Example4-3, the M-OH ratio, the molar absorption coefficients thereof atwavelengths of 200 nm to 380 nm, the average reflectance values thereofat wavelengths of 780 nm to 2500 nm, the transmittance for light rays ata wavelength of 330 nm, the transmittances thereof at wavelengths 380 nmto 780 nm, and the haze value. In addition, the transmittances and molarabsorption coefficients of zinc oxide particles respectively prepared inComparative Example 4-1 to Comparative Example 4-2 were measured usingpropylene glycol as a dispersion medium in a manner similar to Examples1 to 5.

TABLE 36 Comparative Example 4-1 4-2 4-3 Average primary particle 115.6116.2 116.7 diameter [nm] M-OH ratio [%] 8.3 6.5 3.2 Average molarabsorption 231 243 251 coefficient [L/(mol · cm)] (200-380 nm) Averagereflectance [%] 55.9 56.8 57.1 (780-2500 nm) Transmittance [%] 11.1 11.311.5 (330 nm) Average transmittance [%] 76.9 75.1 73.9 (380-780 nm) Hazevalue [%] 2.18 2.11 2.26

As is evident from Table 36, for zinc oxide particles having primaryparticle diameters of more than 100 nm, even if the M-OH ratio ischanged, the molar absorption coefficients at wavelengths from 200 nm to780 nm and the average reflectance values at wavelengths of 780 nm to2500 nm did not change significantly. Under the conditions ofComparative Example 4-1 to Comparative Example 4-3, furthermore, thetransmittance for light rays at a wavelength of 330 nm was 10% or more,the transmittances thereof at wavelengths 380 nm to 780 nm was less than90%, and the haze value exceeded 1%.

Example 7

Subsequently, from the dispersion of zinc oxide particles dischargedfrom the fluid treatment apparatus and collected in the beaker in theExample 5, zinc oxide particles were prepared in a manner similar toExample 1 except that the dispersion was subjected to the dispersionmodifier 100 shown in FIG. 34. Table 37 represents the conditions forcontrolling the ratio of M-OH bonds in the zinc oxide particles usingthe dispersion modifier 100 of FIG. 34. Zinc oxide particles in whichthe ratio of M-OH bonds was controlled were obtained in the same manneras in Examples 1-11 to Example 1-13 except for the contents described inTable 37.

Both the procedures for dispersing the dispersion of zinc oxideparticles and procedures for removal of impurities in the dispersion ofzinc oxide particles were carried out repeatedly until the pH of thedispersion of zinc oxide particles reached 7.01 (measurementtemperature: 23.2° C.) and the conductivity thereof reached 0.04 S/cm.The impurities contained in the aggregates of zin oxide particles werealso removed. Thus, each of the zinc oxide particles in the dispersionthereof was modified.

TABLE 37 Examples 7-1 Processing solution Zinc oxide particle dispersionliquid (1) 1st amount of solution charged into container Type: MeOH 130pH 7.00 (measurement temperature: 23.5° C.) Conductivity 0.01 μS/cm(measurement temperature 23.5° C.) Input: 15 L (ca. 12 kg) (2) Type,flow rate, and temperature of cross flow Type: MeOH cleaning liquid pH7.00 (measurement temperature: 23.5° C.) Conductivity 0.01 μS/cm(measurement temperature 23.5° C.) Flow rate: 0.7 L/min, 24° C. (3)Dispersing machine 102 CLEARMIX (product name: CLM-2. 2S, rotor: R1,screen: S 0.8-48, manufactured by M Technique Co., Ltd.) (4) Removalpart 120 Hollow fiber type dialyzer PN-220 (film area: 2.2 m², material:polysulfone), manufactured by Nikkiso Co., Ltd. (5) Rotor speed 10,000rpm (peripheral speed: 15.7 m/S) (6) Start of charging oxide particledispersion When the first pure water inside the vessel 130 has beenreduced to 1 L (7) Input of oxide particle dispersion into oxide 15 L(ca. 12 kg) container 130 (8) pH of oxide particle dispersion liquidinside more than 14 (measuring temperature: 23.2° C.) vessel 130 (9)Conductivity of oxide particle dispersion liquid 2999 μS/cm (measurementtemperature: 23.2° C.) inside the vessel 130 (10) Flow rate of pump 1048.8 L/min (11) Flow rate oxide particle dispersion liquid is 7.3 L/minreturned to storage container 130 (12) Discharge amount (calculatedvalue) of filtrate 1.5 L/min L3 by removal part 120 (13) Timing ofintroduction of diluent into container When the dispersion amount instorage container 130 is 130 concentrated to 1.5 L (14) Type and inputof 2nd different dilution to Type: MeOH storage container 130 pH 7.00(measurement temperature: 23.5° C.) Conductivity 0.01 μS/cm (measurementtemperature 23.5° C.) Flow rate: 0.7 L/min, 24° C. (15) Concentration ofoxide particles in oxide 1.0 wt % to 10.0 wt % particle dispersion (16)Pressure gauge Pa: Both of two are 0.10 MPaG (17) Pressure gauge Pb:0.15 MPaG (18) Pressure gauge Pc: 0.02 MPaG (19) Path length (Lea) 0.3 m(20) Pipping inner diameter (Leb) 0.0105 m (21) Flow velocity of oxideparticle dispersion liquid 1.2 m/sec in immediately preceding transportpath (22) Time T1 until removal part 120 starts removal 0.24 sec ofimpurities from dispersion container 101 (23) Thermometer placed in thedispersion 23° C. to 26° C. container 101 (24) Temperature of oxideparticle dispersion 23° C. to 26° C. (25) Conductivity measuring machineElectrical conductivity meter, model number ES-51 manufactured byHORIBA, Ltd.

Zinc oxide particles with different M-OH ratios were prepared bychanging the treatment temperature for modifying the dispersion of zincoxide particles shown in (23) and (24) of Table 37. Table 38 represents:the treatment temperature for modifying the dispersion of zinc oxideparticles; the ratio of M-OH in the resulting zinc oxide particles theaverage reflectance values thereof at wavelengths of 780 nm to 2500 nm,the average reflectance value at wavelengths of 380 nm to 780 nm, theaverage transmittance at wavelengths of 380 nm to 780 nm, the molarabsorption coefficients thereof at wavelengths of 200 nm to 380 nm, andthe haze value.

TABLE 38 Example 7-1 7-2 7-3 Average primary particle 8.5 8.5 8.4diameter [nm] Treatment temperature 23-26 43-46 59-61 (Table 37: (23))[° C.] Treatment temperature 23-26 43-4 59-61 (Table 37: (24)) [° C.]M-OH ratio [%] 10.9 9.4 8.8 Average molar absorption 665 712 725coefficient [L/(mol · cm)] (200-380 nm) Average reflectance [%] 69.971.6 73.6 (780-2500 nm) Average transmittance [%] 97.3 97.5 97.6(380-780 nm) Haze value [%] 0.02 0.02 0.02

As is evident from FIG. 38, the lower the ratio of M-OH, the higher theaverage reflectance at wavelengths of 780 nm to 2500 nm, the averagereflectance at wavelengths of 380 nm to 780 nm, the averagetransmittance at wavelengths 380 nm to 780 nm, and the average molarabsorption coefficient at wavelengths of 200 nm to 380 nm tended to beobserved. Thus, it is found that the color characteristics of the oxideparticles can be controlled by controlling the ratio of M-OH.

Example 8

Example 8 describes cerium oxide particles. An oxide raw-material liquid(liquid A) and an oxide precipitation solvent (liquid B) were preparedusing a high-speed rotation-type dispersion emulsifier CLERMIX (productname: CLM-2.2S, manufactured by M Technique Co., Ltd.). Specifically,based on the formulation of the oxide raw-material liquid shown inExample 8 of Table 39, using CLEARMIX at a rotor rotational speed of20,000 rpm, the respective ingredients of the oxide raw-material liquidwere stirred and homogeneously mixed together at a preparationtemperature of 40° C. for 30 minutes to prepare an oxide raw-materialliquid. Also, based on the formulation of the oxide precipitationsolvent shown in Example 8 of Table 39, using CLEARMIX at a rotorrotational speed of 15,000 rpm, the respective ingredients of the oxideraw-material liquid were stirred and homogeneously mixed together at apreparation temperature of 45° C. for 30 minutes to prepare an oxideprecipitation solvent. Regarding substances indicated by chemicalformulas and abbreviations described in Table 39, DMAE used was dimethylaminoethanol (manufactured by Kishida Chemical Co., Ltd.) andCe(NO₃)₃.6H₂O used was cerium (III) nitrate hexahydrate (manufactured byWako Pure Chemical Industries, Ltd.).

Subsequently, the prepared oxide raw-material liquid and oxideprecipitation solvent were mixed together using a fluid treatmentapparatus described in Patent Literature 6 of the present applicant. Amethod for treating each fluid and a method for collecting the treatedliquid were carried out in a manner similar to Example 1. In addition,Example 8 did not use the third introduction portion d3 and liquid C(not shown).

As in the case with Example 1, Table 40 represents the operatingconditions of the fluid treatment apparatus and the average primaryparticle diameter calculated from the results of the TEM observation ofthe resulting cerium oxide particles. The procedures for pH measurement,analysis, and particle-washing were also carried out in the same manneras in Example 1. As a result of the TEM observation, the primaryparticle diameters were approximately 5 nm to 15 nm, and as described inTable 40, the average primary particle diameter was 5.19 nm.

TABLE 39 Example 8 Formulation of the 1st fluid Formulation of the 2ndfluid (liquid A: Oxide precipitation solvent) (liquid B: Oxide rawmaterial liquid) Formulation Formulation Raw Raw pH Raw Raw pH material[wt %] material [wt %] pH [° C.] material [wt %] material [wt %] pH [°C.] DMAE 1.40 Pure 98.60 11.4 26.7 Ce(NO₃)₃ 9.00 Pure 91.00 3.2 29.0water 6H₂O water

TABLE 40 Example 8 Introduction flow Introduction Introduction ratetemperature pressure (liquid feed flow (liquid feed (liquid feed Averagerate) temperature) pressure) Discharged primary [ml/min] [° C.] [MPaG]liquid particle Liquid Liquid Liquid Liquid Liquid Liquid Temp. diameterA B A B A B pH [° C.] [nm] 100 40 135 81 0.333 0.10 7.97 29.6 5.19

The cerium oxide particles obtained in Example 8 were subjected to aheat treatment using an electric furnace to modify the functional groupscontained in the iron oxide particles. The heat treatment conditionswere as follows: untreated in Example 8; 100° C. in Example 8-2; 200° C.in Example 8-3; and 300° C. in Example 8-4. For each heat treatmenttemperature, the duration of heat treatment was 30 minutes. The ceriumoxide particles obtained in Example 8-2 to Example 8-4 also had primaryparticle diameters of approximately 5 nm to 15 nm.

Only the peaks that came from cerium oxide particles (CeO₂) weredetected in the XRD measurement of cerium oxide particles obtained inExample 8 and Example 8-2 to Example 8-4.

Table 41 represents the molar absorption coefficients for light rays atwavelengths of 200 nm to 380 nm together with the ratio of M-OH of thecerium oxide particles obtained in Example 8 and Example 8-2 to Example8-4. As is evident from Table 41, the molar absorption coefficients forlight rays at wavelengths of 200 nm to 380 nm were improved as the M-OHratio decreases in the order of Examples 8, 8-3, and 8-4.

TABLE 41 Example 8 8-2 8-3 8-4 M-OH ratio [%] 12.4 10.8 5.6 3.3 Averagemolar absorption 3655 4074 4159 4218 coefficient [L/(mol · cm)] (200-380nm)

Further, as is evident from Table 41, unlike the silicon compound-coatedcerium oxide particles obtained in Example 3, an M-OH ratio of 11% orless in cerium oxide particles can attain a molar absorption coefficientof 4000 L/(mol·cm) or more for light rays at wavelengths of 200 nm to380 nm. In the present invention, preferable cerium oxide particles arethose in which the ratio of M-OH bonds contained therein is 12.5% orless and the molar absorption coefficient thereof is 3500 L/(mol·cm) ormore at wavelengths of 200 nm to 380 nm. More preferable cerium oxideparticles are those in which the ratio of M-OH bonds contained thereinis 11% or less and the molar absorption coefficient thereof is 4000L/(mol·cm) or more at wavelengths of 200 nm to 380 nm.

Example 8-5 to Example 8-7

Subsequently, from the dispersion of cerium oxide particles dischargedfrom the fluid treatment apparatus and collected in the beaker in theExample 8, cerium oxide particles were prepared in a manner similar toExample 8 except that the dispersion was subjected to the dispersionmodifier 100 shown in FIG. 34. Table 42 represents the conditions forcontrolling the ratio of M-OH bonds in the cerium oxide particles usingthe dispersion modifier 100 of FIG. 34. Cerium oxide particles in whichthe ratio of M-OH bonds was controlled were obtained in the same manneras in Examples 1-11 to Example 1-13 except for the contents described inTable 42.

Both the procedures for dispersing the dispersion of cerium oxideparticles and procedures for removal of impurities in the dispersion ofsilicon compound-coated iron oxide particles were carried out repeatedlyuntil the pH of the dispersion of silicon compound-coated iron oxideparticles reached 7.22 (measurement temperature: 25.6° C.) and theconductivity thereof reached 7.77 μS/cm. The impurities contained in theaggregates of cerium oxide particles were also removed. Thus, each ofthe cerium oxide particles in the dispersion thereof was modified.

TABLE 42 Examples 8-5 Processing solution Cerium oxide particledispersion liquid (1) 1st amount of solution charged into containerType: Pure water 130 pH 5.89 (measurement temperature: 22.4° C.)Conductivity 0.80 μS/cm (measurement temperature 22.4° C.) Input: 15 kg(2) Type, flow rate, and temperature of cross flow Type: Pure watercleaning liquid pH 5.89 (measurement temperature: 22.4° C.) Conductivity0.80 μS/cm (measurement temperature 22.4° C.) Flow rate: 1.5 L/min, 21°C. (3) Dispersing machine 102 CLEARMIX (product name: CLM-2. 2S, rotor:R1, screen: S 0.8-48, manufactured by M Technique Co., Ltd.) (4) Removalpart 120 Hollow fiber type dialyzer PN-220 (film area: 2.2 m², material:polysulfone), manufactured by Nikkiso Co., Ltd. (5) Rotor speed 20,000rpm (peripheral speed: 31.4 m/S) (6) Start of charging oxide particledispersion When the first pure water inside the vessel 130 has beenreduced to 1 L (7) Input of oxide particle dispersion into oxide 14 L(ca. 14 kg) container 130 (8) pH of oxide particle dispersion liquidinside 7.69 (measuring temperature: 26.6° C.) vessel 130 (9)Conductivity of oxide particle dispersion liquid 3131 μS/cm (measurementtemperature: 26.6° C.) inside the vessel 130 (10) Flow rate of pump 1048.8 L/min (11) Flow rate oxide particle dispersion liquid is 7.3 L/minreturned to storage container 130 (12) Discharge amount (calculatedvalue) of filtrate 1.5 L/min L3 by removal part 120 (13) Timing ofintroduction of diluent into container When the dispersion amount instorage container 130 is 130 concentrated to 1.5 L (14) Type and inputof 2nd different dilution to Type: Pure water storage container 130 pH5.89 (measurement temperature: 22.4° C.) Conductivity 0.80 μS/cm(measurement temperature 22.4° C.) Input: 13.5 L (ca. 13.5 kg) (15)Concentration of oxide particles in oxide 0.4 wt % to 2.0 wt % particledispersion (16) Pressure gauge Pa: Both of two are 0.10 MPaG (17)Pressure gauge Pb: 0.15 MPaG (18) Pressure gauge Pc: 0.02 MPaG (19) Pathlength (Lea) 0.3 m (20) Pipping inner diameter (Leb) 0.0105 m (21) Flowvelocity of oxide particle dispersion liquid 1.2 m/sec in immediatelypreceding transport path (22) Time T1 until removal part 120 startsremoval 0.24 sec of impurities from dispersion container 101 (23)Thermometer placed in the dispersion 23° C. to 26° C. container 101 (24)Temperature of oxide particle dispersion 23° C. to 26° C. (25)Conductivity measuring machine Electrical conductivity meter, modelnumber ES-51 manufactured by HORIBA, Ltd.

By changing the treatment temperature in the modification of thedispersion of cerium oxide particles shown in (23) and (24) of Table 42,cerium oxide particles having different ratios of M-OH were prepared asthose of Example 8-5 to Example 8-7. Table 43 represents, together withthe results of Example 8, the treatment temperature for modifying thedispersion of cerium oxide particles, the ratio of M-OH in the resultingcerium oxide particles, and the molar absorption coefficients thereof atwavelengths of 200 nm to 380 nm.

TABLE 43 Example 8 8-5 8-6 8-7 Treatment temperature — 23-26 43-46 59-61(Table 42: (23)) [° C.] Treatment temperature — 23-26 43-46 59-61 (Table42: (24)) [° C.] M-OH ratio [%] 12.4 11.8 10.6 7.9 Average molarabsorption 3655 3888 4092 4123 coefficient [L/(mol · cm)] (200-380 nm)

As is evident from Table 43, the lower the ratio of M-OH the higher themolar absorption coefficient at wavelengths of 200 nm to 380 nm tendedto be observed. Thus, it is found that the color characteristics of theoxide particles can be controlled by controlling the ratio of M-OH.

Comparative Example 5

Cerium oxide particles (special grade iron oxide (IV) (CeO₂)manufactured by Wako Pure Chemical Industries, Ltd.) having primaryparticle diameters of 120 nm to 200 nm were subjected to a heattreatment in an electric furnace to modify the functional groupscontained in the cerium oxide particles for changing the ratio of M-OHbonds. The heat treatment conditions were as follows: untreated inComparative Example 1-1; 100° C. in Comparative Example 1-2; and 300° C.in Comparative Example 1-3. For each heat treatment temperature, theduration of heat treatment was 30 minutes. For iron oxide particles ofComparative Examples 1-1 to 1-3, Table 44 represents the ratio of M-OHand the molar absorption coefficient for light rays at wavelengths of200 nm to 380 nm in a dispersion in which the iron oxide particles weredispersed in a manner similar to Example 8. As is evident from Table 44,in the case of cerium oxide particles having primary particle diametersof more than 50 nm or more, even when the ratio of M-OH bonds waschanged, the molar absorption coefficient was low, resulting in noobserved increasing tendency. In comparison between Comparative Example5-1 and Example 8-4 in particular, even the cerium oxide particles havethe ratio of M-OH similar to the iron oxide particles having primaryparticle diameters of 50 nm or less obtained in Example 8-4, it is foundthat the iron oxide particles of Comparative Example 5-1 have lowermolar absorption coefficients in a region at wavelengths of 200 nm to380 nm. In the present invention, when the primary particle diameter isas small as 50 nm or less, the ratio of M-OH affects the colorcharacteristics. That is, in a state where the surface area is increasedwith respect to the same amount of cerium oxide particles, colorcharacteristics can be controlled by controlling the M-OH ratio.

TABLE 44 Comparative Example 5-1 5-2 5-3 M-OH ratio [%] 7.3 3.2 1.9Average molar absorption 946 951 933 coefficient [L/(mol · cm)] (190-380nm)

Example 9 to Example 11

Examples 9 to 11 describe cobalt-zinc-complex oxide particles as oxideparticles, which is an oxide comprising cobalt and zinc. An oxideraw-material liquid (liquid A) and an oxide precipitation solvent(liquid B) were prepared using a high-speed rotation-type dispersionemulsifier CLERMIX (product name: CLM-2.2S, manufactured by M TechniqueCo., Ltd.). Specifically, based on the formulation of the oxideraw-material liquid shown in Example 9 in Table 45, the ingredients ofthe oxide raw-material liquid were homogeneously mixed by stirring themat 20,000 rpm for 30 minutes at a preparation temperature of 40° C.using CLEARMIX to prepare an oxide raw-material liquid. Based on theformulation of the oxide precipitation solvent shown in Example 9 inTable 45, the ingredients of the oxide raw-material liquid werehomogeneously mixed by stirring them at 15,000 rpm for 30 minutes at apreparation temperature of 45° C. using CLEARMIX to prepare an oxideprecipitation solvent. Regarding substances indicated by chemicalformulas and abbreviations described in Table 45, EG used was ethyleneglycol (manufactured by Kishida Chemical Co., Ltd.), Zn(NO₃)₂.6H₂O usedwas zinc nitrate hexahydrate (manufactured by Wako Pure ChemicalIndustries, Ltd.), Co (NO₃)₂.6H₂O used was cobalt nitrate hexahydrate(manufactured by Wako Pure Chemical Industries, Ltd.), and NaOH used wassodium hydroxide (manufactured by KANTOCHEMICAL CO., LTD.).

Subsequently, the prepared oxide raw-material liquid and the oxideprecipitation solvent were mixed together using a fluid treatmentapparatus described in Patent Literature 6 of the present applicant. Amethod for treating each fluid and a method for collecting the treatedliquid were carried out in a manner similar to Example 1. In Examples 9to 11, furthermore, third foreword d3 and liquid C were not used (notshown).

Table 46 represents the operating conditions of the fluid treatmentapparatus, the average primary particle diameters calculated from theTEM observation results of the obtained cobalt-zinc-complex oxideparticles, the molar ratios of Co/Zn calculated from TEM-EDS analysis,and calculated values calculated from the formulations and introductionflow rates of liquid A, liquid B, and liquid C. The procedures for pHmeasurement, analysis, and particle-washing were also carried out in thesame manner as in Example 1.

TABLE 45 Formulation of the 1st fluid Formulation of the 2nd fluid(liquid A: Oxide raw material liquid) (liquid B: Oxide precipitationsolvent) Formulation Formulation Raw Raw Raw pH Raw Raw pH Examplematerial [wt %] material [wt %] material [wt %] pH [° C.] material [wt%] material [wt %] pH [° C.]  9 Zn(NO₃)₂ 3.0000 Co(NO₃)₃ 0.0447 EG96.955 4.21 21.9 NaOH 9.00 Pure 91.00 >14 — 6H₂O 6H₂O water 10 Zn(NO₃)₂3.0000 Co(NO₃)₃ 0.3650 EG 96.635 4.10 22.2 NaOH 9.00 Pure 91.00 >14 —6H₂O 6H₂O water 11 Zn(NO₃)₂ 3.0000 Co(NO₃)₃ 0.9783 EG 96.022 3.87 23.1Na011 9.00 Pure 91.00 >14 — 6H₂O 6H₂O water

TABLE 46 Introduction Introduction Introduction flow rate temperaturepressure (liquid feed (liquid feed (liquid feed Average flow rate)temperature) pressure) Discharged Co/Zn primary [ml/min] [° C.] [MPaG]liquid [Molar ratio] particle Liquid Liquid Liquid Liquid Liquid LiquidTemp. Calc. diameter Example A B A B A B pH [° C.] value EDS [nm] 9 40045 160 87 0.103 0.10 11.87 29.3 0.02 0.02 9.79 10 400 45 159 87 0.0930.10 11.86 28.8 0.11 0.11 9.89 11 400 50 161 86 0.087 0.10 11.78 28.90.33 0.33 10.16

FIG. 62 represents the result of mapping with the STEM ofcobalt-zinc-complex oxide particles obtained in Example 9, and FIG. 63represents the results of the line analysis at the position indicated bythe broken line in the BF image (bright field image) of FIG. 62. FIG. 64represents the result of mapping with the STEM of cobalt-zinc-complexoxide particles obtained in Example 11, and FIG. 65 represents theresult of the line analysis at the position indicated by the broken linein the BF image (bright field image) of FIG. 64. As is evident fromFIGS. 62 to 65, in the cobalt-zinc-complex oxide particles obtained inExample 9 and Example 11, cobalt and zinc were detected in the entireparticles. The cobalt-zinc-complex oxide particles were observed asthose in which cobalt and zinc were solid-solved uniformly. Similarparticles were also observed in Examples 9-2, 9-3, 10, 10-2, 10-3, 11-2,and 11-3 described later.

The cobalt-zinc-complex oxide particles obtained in Examples 9 to 11were subjected to a heat treatment with an electric furnace to modifythe functional groups contained in the cobalt-zinc-complex oxideparticles. The heat treatment conditions were as follows: untreated inExamples 9, 10, and 11; 100° C. in Examples 9-2, 20-2, and 11-2; 200° C.in Examples 9-3, 10-3, and 11-3; and 300° C. in Examples 10-4 and 11-4.For each heat treatment temperature, the duration of heat treatment was30 minutes.

FIG. 66 represents transmission spectra of dispersions in whichcobalt-zinc-complex oxide particles obtained in Examples 9, 10, and 11were respectively dispersed at a concentration of 0.05 wt % in propyleneglycol for light rays at wavelengths of 380 nm to 780 nm. FIG. 67represents reflection spectra of the powders of cobalt-zinc-complexoxide particles obtained in Examples 9, 10, and 11 for light rays atwavelengths of 200 nm to 780 nm. As is evident from the figure, thecobalt-zinc-complex oxide particles exhibit colors of green to lightblue.

In Table 47 for the cobalt-zinc-complex oxide particles obtained inExample 9 and Examples 9-2 to 9-4, Table 48 for Example 10 and Examples10-2 to 10-4, and Table 49 for Example 11 and Examples 11-2 to 11-4, theratio of M-OH contained in the particles, the absorption spectrum of thedispersion in which cobalt-zinc-complex oxide particles were dispersedin propylene glycol and the molar absorption coefficient for light raysat wavelengths of 200 nm to 380 nm calculated from the concentration ofcobalt-zinc-complex oxide particles (as ZnO+Co) in a measurement liquidare represented. For comparison, the zinc oxide particles obtained inExample 5 are also shown.

TABLE 47 Example 5 9 9-2 9-3 9-4 M-OH ratio [%] 11.8 12.4 7.9 3.1 1.2Average molar absorption 623 781 896 923 999 coefficient [L/(mol · cm)](200-380 nm)

TABLE 48 Example 5 10 10-2 10-3 10-4 M-OH ratio [%] 11.8 12.5 7.9 3.11.2 Average molar absorption 623 779 879 919 987 coefficient [L/(mol ·cm)] (200-380 nm)

TABLE 49 Example 5 11 11-2 11-3 11-4 M-OH ratio [%] 11.8 19.9 5.4 1.10.8 Average molar absorption 623 772 864 906 979 coefficient [L/(mol ·cm)] (200-380 nm)

As is evident from Tables 47 to 49, the cobalt-zinc-complex oxideparticles also improved the molar absorption coefficient for light raysat wavelengths of 200 nm to 380 nm as the ratio of M-OH bonds containedin the particles became lower. Preferably, furthermore, thecobalt-zinc-complex oxide particles have the ratio of M-OH bondscontained therein of 0.5% or more and 20% less to make the molarabsorption coefficient 700 L/(mol·cm) for light rays at wavelengths of200 nm to 380 nm. It is also found that the cobalt-zinc-complex oxideparticles have a higher molar absorption coefficient for light rays atwavelengths of 200 nm to 380 nm than zinc oxide particles. Thecobalt-zinc-complex oxide particles with the controlled ratio of M-OHbonds exhibit color of green to light blue. Thus, thecobalt-zinc-complex oxide particles can be effectively used for thepurpose of transparency or ultraviolet-shielding ability when used in afilm-like composition, such as a coated product or glass.

Example 12 to Example 14

Examples 12 to 14 describe silicon-cobalt-zinc-complex oxide particlesas oxide particles. An oxide raw-material liquid (liquid A) and an oxideprecipitation solvent (liquid B) were prepared using a high-speedrotation-type dispersion emulsifier CLERMIX (product name: CLM-2.2S,manufactured by M Technique Co., Ltd.). Specifically, based on theformulation of the oxide raw-material liquid shown in Examples 12 to 14in Table 50, the ingredients of the oxide raw-material liquid werehomogeneously mixed by stirring them at a rotor speed of 20,000 rpm for30 minutes at a preparation temperature of 40° C. using CLEARMIX toprepare an oxide raw-material liquid. Also, based on the formulation ofthe oxide precipitation solvent shown in Examples 12 to 14 in Table 50,the ingredients of the oxide raw-material liquid were homogeneouslymixed by stirring them at a rotor speed of 15,000 rpm for 30 minutes ata preparation temperature of 45° C. using CLEARMIX to prepare an oxideprecipitation solvent. Furthermore, based on the formulation of thesilicon compound-coated iron oxide particles show in Examples 12 to 14of Table 50, using CLEARMIX at a rotor speed of 6,000 rpm, therespective ingredients of the silicon compound-coated iron oxideparticles were stirred and homogeneously mixed together at a preparationtemperature of 20° C. for 10 minutes to prepare silicon compound-coatediron oxide particles.

Regarding substances indicated by chemical formulas and abbreviationsdescribed in Table 50, EG used was ethylene glycol (manufactured byKishida Chemical Co., Ltd.), Zn(NO₃)₂.6H₂O used was zinc nitratehexahydrate (manufactured by Wako Pure Chemical Industries. Co(NO₃)₂.6H₂O used was cobalt nitrate hexahydrate (manufactured by WakoPure Chemical Industries, Ltd.), NaOH used was sodium hydroxide(manufactured by KANTOCHEMICAL CO., LTD.), 60 wt % HNO₃ used wasconcentrated nitric acid (manufactured by Kishida Chemical Co., Ltd.),and TEOS used was tetraethyl orthosilicate (manufactured by Wako PureChemical Industries, Ltd.).

Subsequently, the prepared oxide raw-material liquid, oxideprecipitation solvent, and silicon compound-coated iron oxide particleswere mixed together using a fluid treatment apparatus described inPatent Literature 6 of the present applicant. A method for treating eachfluid and a method for collecting the treated liquid were carried out ina manner similar to Example 1.

Table 51 represents the operating conditions of the fluid treatmentapparatus, the average primary particle diameters calculated from theTEM observation results of the obtained silicon compound-coated ironoxide particles, the molar ratios of Si/Co/Zn calculated from TEM-EDSanalysis, and calculated values calculated from the formulations andintroduction flow rates of liquid A, liquid B, and liquid C. Theprocedures for pH measurement, analysis, and particle-washing were alsocarried out in the same manner as in Example 1.

TABLE 50 Formulation of the 1st fluid Formulation of the 2nd fluid(liquid A: Oxide raw material liquid) (liquid B: Oxide precipitationsolvent) Formulation Formulation Raw Raw Raw pH Raw Raw pH Examplematerial [wt %] material [wt %] material [wt %] pH [° C.] material [wt%] material [wt %] pH [° C.] 12 Zn(NO₂)₂ 3.0000 CO(NO₃)₃ 0.0447 EG96.955 4.21 21.9 NaOH 9.00 Pure 91.00 >14 — 6H₂O 6H₂O water 13 Zn(NO₂)₂3.0000 CO(NO₃)₃ 0.3650 EG 96.635 4.10 22.2 NaOH 9.00 Pure 91.00 >14 —6H₂O 6H₂O water 14 Zn(NO₂)₂ 3.0000 CO(NO₃)₃ 0.9783 EG 96.022 3.87 23.1NaOH 9.00 Pure 91.00 >14 — 6H₂O 6H₂O water Formulation of the 3rd fluid(liquid C: Silicon compound raw material liquid) Formulation Raw Raw RawRaw pH Example material [wt %] material [wt %] material [wt %] material[wt %] pH [° C.] 12 Pure 9.4222 EG 90.0000 60% 0.0100 TEOS 0.5678 2.1315.9 water HNO₃ 13 Pure 9.4222 EG 90.0000 60% 0.0100 TEOS 0.5678 2.1315.9 water HNO₃ 14 Pure 9.4222 EG 90.0000 60% 0.0100 TEOS 0.5678 2.1315.9 water HNO₃

TABLE 51 Introduction temperature Introduction flow rate (liquid feedIntroduction pressure Average (liquid feed flow rate) temperature)(liquid feed pressure) Discharged primary [ml/min] [° C.] [MPaG] liquidSi/Co/Zn particle Ex- Liquid Liquid Liquid Liquid Liquid Liquid LiquidLiquid Liquid Temp. [Molar ratio] diameter ample A B C A B C A B C pH [°C.] Calc. value EDS [nm] 12 400 39 100 160 86 25 0.068 0.10 0.10 10.9520.8 20.7/1.2/78.1 20.7/1.2/78.1 9.64 13 400 40 100 161 85 25 0.065 0.100.10 10.02 22.6 19.3/8.1/72.6 19.3/8.1/72.6 9.57 14 400 49 100 160 87 250.071 0.10 0.10  8.34 22.3 16.7/20.8/ 16.7/20.8/ 9.34 62.5 62.5

FIG. 68 represents the result of mapping with the STEM ofsilicon-cobalt-zinc-complex oxide particles obtained in Example 13, andFIG. 69 represents the result of the line analysis at the positionindicated by the broken line in the BF image (bright field image) ofFIG. 68. As is evident from FIGS. 68 to 69, in thesilicon-cobalt-zinc-complex oxide particles obtained in Example 13,silicon, cobalt, zinc, and oxygen were detected in the entire particles.The cobalt-zinc-complex oxide particles were observed as those in whichcobalt and zinc were solid-solved uniformly. Similar particles were alsoobserved in Examples 12, 12-2, 13-2, 13-3, 14, 14-2, and 14-3 describedlater.

The silicon-cobalt-zinc-complex oxide particles obtained in Examples 12to 14 were subjected to a heat treatment with an electric furnace tomodify the functional groups contained in thesilicon-cobalt-zinc-complex oxide particles. The heat treatmentconditions were as follows: untreated in Examples 12, 13, and 14; 100°C. in Examples 12-2, 13-2, and 14-2; 200° C. in Examples 12-3, 13-3, and14-3; and 300° C. in Examples 12-4, 13-4, and 14-4. For each heattreatment temperature, the duration of heat treatment was 30 minutes.

FIG. 70 represents reflection spectra of the powders ofsilicon-cobalt-zinc-complex oxide particles obtained in Examples 12, 13,and 14 for light rays at wavelengths of 200 nm to 780 nm, and, as acomparison, the results of the powders of cobalt-zinc-complex oxideparticles obtained in Example 9, Example 10, and Example 11 and havingthe same Co/Zn (molar ratio) contained therein. As is evident from thefigure, in contrast to the cobalt-zinc-complex oxide particles (Example9 to Example 11) exhibiting color of light blue to green, thesilicon-cobalt-zinc-complex oxide particles (Examples 12 to 14) emittedstronger blue color because of their high reflectance for light rays atwavelengths of 400 nm to 450 nm.

With respect to the ratio of M-OH contained in the particles, theabsorption spectra of dispersions in which silicon-cobalt-zinc-complexoxide particles were dispersed in propylene glycol, and the molarabsorption coefficients for light rays at wavelengths of 200 nm to 380nm calculated from the concentrations of the cobalt-zinc-complex oxideparticles (as ZnO+Co) in measurement liquids of the respective examples,Table 52 represents the silicon-cobalt-zinc-complex oxide particlesobtained in Example 12 and Examples 12-2 to 12-4 and thecobalt-zinc-complex oxide particles of Example 9 having the same Co/Zn(molar ratio) as the former but do not contain silicon,

Table 53 represents the silicon-cobalt-zinc-complex oxide particlesobtained in Example 13 and Examples 13-2 to 13-4 and thecobalt-zinc-complex oxide particles of Example 10 having the same Co/Zn(molar ratio) as the former but do not contain silicon, and Table 54represents the silicon-cobalt-zinc-complex oxide particles obtained inExample 14 and Examples 14-2 to 14-4 and the cobalt-zinc-complex oxideparticles of Example 11 having the same Co/Zn (molar ratio) as theformer but do not contain silicon. For comparison, the zinc oxideparticles obtained in Example 5 are also shown.

TABLE 52 Example 9 12 12-2 12-3 12-4 M-OH ratio [%] 12.4 28.4 18.4 16.913.1 Average molar absorption 781 849 931 1009 1126 coefficient [L/(mol· cm)] (200-380 nm)

TABLE 53 Example 10 13 13-2 13-3 13-4 M-OH ratio [%] 12.5 25.9 18.6 15.113.3 Average molar absorption 779 841 925 1023 1159 coefficient [L/(mol· cm)] (200-380 nm)

TABLE 54 Example 11 14 14-2 14-3 14-4 M-OH ratio [%] 19.9 32.1 25.4 23.120.6 Average molar absorption 772 834 819 1064 1202 coefficient [L/(mol· cm)] (200-380 nm)

As is evident from Tables 52 to 54, the silicon-cobalt-zinc-complexoxide particles also improved the molar absorption coefficient for lightrays at wavelengths of 200 nm to 380 nm as the ratio of M-OH bondscontained in the particles became lower. Preferably, furthermore, thesilicon-cobalt-zinc-complex oxide particles have the ratio of M-OH bondscontained therein of 13% or more and 33% or less to make the molarabsorption coefficient 800 L/(mol·cm) for light rays at wavelengths of200 nm to 380 nm. It is also found that the silicon-cobalt-zinc-complexoxide particles have a higher molar absorption coefficient for lightrays at wavelengths of 200 nm to 380 nm than cobalt-zinc-complex oxideparticles. Furthermore, the silicon-cobalt-zinc-complex oxide particleswith the controlled ratio of M-OH bonds exhibit color of light blue toblue (blue green). Thus, the cobalt-zinc-complex oxide particles can beeffectively used for the purpose of transparency orultraviolet-shielding ability when used in a film-like composition, suchas a coated product or glass.

According to the present invention, as described above, the colorcharacteristics of oxide particles can be delicately and strictlycontrolled. Hence, when used in a coating or film-like composition, theoxide particles can strictly control transmission, absorption, hue,color saturation, and molar absorption coefficient for light rays in theultraviolet, visible, and near infrared regions. When applied to thehuman body, the oxide particles do not impair the texture and beauty.When used for a coating body or used in the shape of a film for glass orthe like, the oxide particles can protect the human body and paintedbody from ultraviolet rays and near infrared rays without damaging thedesign.

The invention claimed is:
 1. Silicon compound-coated oxide particles inwhich at least a part of the surface of the oxide particles is coatedwith a silicon compound, wherein the oxide contained in the oxideparticles is iron oxide, and the silicon compound is able to change thecolor characteristics of the oxide particles by coating at least a partof the surface of the oxide particles, and wherein the ratio of M-OHbonds contained in the oxide particles is 8% or more and 14.5% or less,the average reflectance of the oxide particles for light rays atwavelengths of 780nm to 2500 nm is 50% or more.
 2. Siliconcompound-coated oxide particles in which at least a part of the surfaceof the oxide particles is coated with a silicon compound, according toclaim 1, wherein the oxide contained in the oxide particles is ironoxide, and the silicon compound is able to change the colorcharacteristics of the oxide particles by coating at least partially thesurface of the oxide particles, and wherein the ratio of M-OH bondscontained in the oxide particles is 10% or more and 14.5% or less, andthe maximum reflectance of the oxide particles for light rays at awavelength of 400 nm to 620 nm is 18% or less.
 3. Siliconcompound-coated oxide particles in which at least a part of the surfaceof the oxide particles is coated with a silicon compound, according toclaim 1, wherein the oxide contained in the oxide particles is ironoxide, and the silicon compound is able to change the colorcharacteristics of the oxide particles by coating at least partially thesurface of the oxide particles, and wherein the ratio of M-OH bondscontained in the oxide particles is 9.5% or more and 13% or less, andthe average reflectance of the oxide particles for light rays atwavelengths of 620 nm to 750 nm is 22% or less.
 4. Siliconcompound-coated oxide particles in which at least a part of the surfaceof the oxide particles is coated with a silicon compound, according toclaim 1, wherein the oxide contained in the oxide particles is ironoxide, and the silicon compound is able to change the colorcharacteristics of the oxide particles by coating at least partially thesurface of the oxide particles, and wherein the ratio of M-OH bondscontained in the oxide particles is 8% or more and 14.5% or less, andhue H(=b*/a*) in an L*a*b* colorimetric system is in the range of 0.5 to0.9.
 5. Silicon compound-coated oxide particles in which at least a partof the surface of the oxide particles is coated with a silicon compound,according to claim 1, wherein the oxide contained in the oxide particlesis iron oxide, and the silicon compound is able to change the colorcharacteristics of the oxide particles by coating at least partially thesurface of the oxide particles, and wherein the ratio of M-OH bondscontained in the oxide particles is 9% or more and 14.5% or less, and,in a transmission spectrum of a dispersion in which the oxide particlesare dispersed in a dispersion medium, the transmittance for light raysat a wavelength of 380 nm is 5% or less and the transmittance for lightrays at a wavelength of 600 nm is 80% or more.
 6. Siliconcompound-coated oxide particles in which at least a part of the surfaceof the oxide particles is coated with a silicon compound, according toclaim 1, wherein the oxide contained in the oxide particles is ironoxide, and the silicon compound is able to change the colorcharacteristics of the oxide particles by coating at least partially thesurface of the oxide particles, and wherein, the ratio of M-OH bondscontained in the oxide particles is 9% more and 14.5% or less, and, in adispersion in which the oxide particles are dispersed in a dispersionmedium, an average molar absorption coefficient for light rays atwavelengths of 190 nm to 380 nm is 2200 L/(mol·cm) or more.
 7. Siliconcompound-coated oxide particles in which at least a part of the surfaceof the oxide particles is coated with a silicon compound, according toclaim 1, wherein the oxide contained in the oxide particles is ironoxide, and the silicon compound is able to change the colorcharacteristics of the oxide particles by coating at least partially thesurface of the oxide particles, and wherein the oxide particles includeester bonds, and the ratio of M-OH bonds contained in the oxideparticles is 9% or more and 13% or less, and the average reflectance ofthe oxide particles for light rays at wavelengths of 780 nm to 2500 nmis 50% or more.
 8. Silicon compound-coated oxide particles in which atleast a part of the surface of the oxide particles is coated with asilicon compound, according to claim 1, wherein the oxide contained inthe oxide particles is iron oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, and wherein theratio of M-OH bonds contained in the oxide particles is 8% or more and9.3% or less, or 13.3% or more and 14.5% or less, and the averagereflectance of the oxide particles for light rays at wavelengths of 620nm to 750 nm is higher than 22%.
 9. The oxide particles according toclaim 1, wherein the oxide particles are oxide particles in which atleast a part of the surface of a single oxide particle or at least apart of the surface of an aggregate formed by aggregation of a pluralityof oxide particles is coated with a silicon compound, and the particlediameter of the oxide particle or the aggregate of oxide particle is 1nm or more and 50 nm or less.
 10. The oxide particles according to claim1, wherein the silicon compound comprises amorphous silicon oxide.
 11. Amethod for producing the oxide particles of claim 1, comprisingcontrolling color characteristics of the oxide particles by controllingthe ratio of M-OH bonds, the binding of one or more different elements(M) other than oxygen or hydrogen with hydroxyl group (OH) in oxideparticles selected from metal oxide particles and metalloid oxideparticles, wherein the ratio of M-OH bonds contained in the oxideparticles is controlled by modifying a functional group contained in theoxide particles, and wherein the modification of the functional group isesterification.
 12. The method for producing oxide particles accordingto claim 11, wherein the modification of the functional group is any oneof an addition reaction, an elimination reaction, a dehydrationreaction, and a displacement reaction.
 13. A method for producing oxideparticles according to claim 11, comprising controlling colorcharacteristics of the oxide particles by controlling the ratio of M-OHbonds, the binding of one or more different elements (M) other thanoxygen or hydrogen with hydroxyl group (OH) in oxide particles selectedfrom metal oxide particles and metalloid oxide particles, wherein theratio of M-OH bonds is controlled using a dispersion-improving apparatuscomprising a removal unit with a membrane filter.
 14. A method forproducing oxide particles according to claim 11, comprising controllingcolor characteristics of the oxide particles by controlling the ratio ofM-OH bonds, the binding of one or more different elements (M) other thanoxygen or hydrogen with hydroxyl group (OH) in oxide particles selectedfrom metal oxide particles and metalloid oxide particles, wherein theratio of M-OH bonds is controlled by a state of a dispersion in whichthe oxide particles are dispersed in a dispersion medium, and whereinthe dispersion is in the form of a coating film, and the colorcharacteristics of the oxide particles are controlled by subjecting thecoating film-like dispersion to a heat treatment.
 15. A method forproducing oxide particles according to claim 11, comprising controllingcolor characteristics of the oxide particles by controlling the ratio ofM-OH bonds, the binding of one or more different elements (M) other thanoxygen or hydrogen with hydroxyl group (OH) in oxide particles selectedfrom metal oxide particles and metalloid oxide particles, wherein theaverage reflectance for light rays at wavelengths of 780 nm to 2500 nmis controlled to be high by controlling the area ratio of thewaveform-separated peak derived from the M-OH bonds to the total area ofeach waveform-separated peak to be low.
 16. A method for producing oxideparticles according to claim 11, comprising controlling colorcharacteristics of the oxide particles by controlling the ratio of M-OHbonds, the binding of one or more different elements (M) other thanoxygen or hydrogen with hydroxyl group (OH) in oxide particles selectedfrom metal oxide particles and metalloid oxide particles, wherein anaverage molar absorption coefficient for light rays at wavelengths of190 nm to 380 nm is controlled to be high by controlling the area ratioof the waveform-separated peak derived from the M-OH bonds to the totalarea of each waveform-separated peak to be low.
 17. Siliconcompound-coated oxide particles in which at least a part of the surfaceof the oxide particles is coated with a silicon compound, wherein theoxide contained in the oxide particles is zinc oxide, and the siliconcompound is able to change the color characteristics of the oxideparticles by coating at least partially the surface of the oxideparticles, and wherein the ratio of M-OH bonds contained in the oxideparticles is 30% or more and 39% or less, and the average reflectance ofthe oxide particles for light rays at wavelengths of 780 nm to 2500 nmis 72% or more.
 18. Silicon compound-coated oxide particles in which atleast a part of the surface of the oxide particles is coated with asilicon compound, according to claim 17, wherein the oxide contained inthe oxide particles is zinc oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, and wherein theratio of M-OH bonds contained in the oxide particles is 30% or more and36% or less, and a wavelength at which the reflectance of the oxideparticles is 15% is 375 nm or more.
 19. Silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, according to claim 17, wherein theoxide contained in the oxide particles is zinc oxide, and the siliconcompound is able to change the color characteristics of the oxideparticles by coating at least partially the surface of the oxideparticles, and wherein the ratio of M-OH bonds contained in the oxideparticles is 38% or more and 39% or less, and an average reflectance forlight rays at wavelengths of 380 nm to 780 nm is 86% or more. 20.Silicon compound-coated oxide particles in which at least a part of thesurface of the oxide particles is coated with a silicon compound,according to claim 17, wherein the oxide contained in the oxideparticles is zinc oxide, and the silicon compound is able to change thecolor characteristics of the oxide particles by coating at leastpartially the surface of the oxide particles, and wherein the ratio ofM-OH bonds contained in the oxide particles is 31% or more and 39% orless, and a color saturation C(=((a*)²+(b*)²)^(1/2)) in an L*a*b*colorimetric system is in the range of 0.5 to
 13. 21. Siliconcompound-coated oxide particles in which at least a part of the surfaceof the oxide particles is coated with a silicon compound, according toclaim 17, wherein the oxide contained in the oxide particles is zincoxide, and the silicon compound is able to change the colorcharacteristics of the oxide particles by coating at least partially thesurface of the oxide particles, and wherein the ratio of M-OH bondscontained in the oxide particles is 38% or more and 39% or less, and, ina transmission spectrum of a dispersion in which the oxide particles aredispersed in a dispersion medium, the transmittance for light rays at awavelength of 340 nm is 10% or less and the average transmittance forlight rays at wavelengths of 380 nm to 780 nm is 92% or more. 22.Silicon compound-coated oxide particles in which at least a part of thesurface of the oxide particles is coated with a silicon compound,according to claim 17, wherein the oxide contained in the oxideparticles is zinc oxide, and the silicon compound is able to change thecolor characteristics of the oxide particles by coating at leastpartially the surface of the oxide particles, and wherein the ratio ofM-OH bonds contained in the oxide particles is 30% or more and 36% orless, and, in a transmission spectrum of a dispersion in which the oxideparticles are dispersed in a dispersion medium, a wavelength at whichthe reflectance of the oxide particles is 15% is 365 nm or more. 23.Silicon compound-coated oxide particles in which at least a part of thesurface of the oxide particles is coated with a silicon compound,according to claim 17, wherein the oxide contained in the oxideparticles is zinc oxide, and the silicon compound is able to change thecolor characteristics of the oxide particles by coating at leastpartially the surface of the oxide particles, and wherein the ratio ofM-OH bonds contained in the oxide particles is 30% or more and 42% orless, and, in a dispersion in which the oxide particles are dispersed ina dispersion medium, an average molar absorption coefficient for lightrays at wavelengths of 200 nm to 380nm is 700L/(mol·cm) or more. 24.Silicon compound-coated oxide particles in which at least a part of thesurface of the oxide particles is coated with a silicon compound,according to claim 17, wherein the oxide contained in the oxideparticles is zinc oxide, and the silicon compound is able to change thecolor characteristics of the oxide particles by coating at leastpartially the surface of the oxide particles, and wherein the ratio ofM-OH bonds contained in the oxide particles is 31% or more and 39% orless, a color saturation C(=((a*)²+(b*)²)^(1/2)) in an L*a*b*colorimetric system is in the range of 0.5 to 13, and an L* value in theL*a*b* colorimetric system is in the range of 95 to
 97. 25. The oxideparticles according to claim 17, wherein the oxide particles are oxideparticles in which at least a part of the surface of a single oxideparticle or at least a part of the surface of an aggregate formed byaggregation of a plurality of oxide particles is coated with a siliconcompound, and the particle diameter of the oxide particle or theaggregate of oxide particle is 1 nm or more and 50 nm or less.
 26. Theoxide particles according to claim 17, wherein the silicon compoundcomprises amorphous silicon oxide.
 27. Silicon compound-coated oxideparticles in which at least a part of the surface of the oxide particlesis coated with a silicon compound, wherein the oxide contained in theoxide particles is cerium oxide, and the silicon compound is able tochange the color characteristics of the oxide particles by coating atleast partially the surface of the oxide particles, and wherein theratio of M-OH bonds contained in the oxide particles is 25% or more and35% or less, and in a dispersion in which the oxide particles aredispersed in a dispersion medium, an average molar absorptioncoefficient for light rays at wavelengths of 200 nm to 380nm is 4000L/(mol·cm) or more.
 28. The oxide particles according to claim 27,wherein the oxide particles are oxide particles in which at least a partof the surface of a single oxide particle or at least a part of thesurface of an aggregate formed by aggregation of a plurality of oxideparticles is coated with a silicon compound, and the particle diameterof the oxide particle or the aggregate of oxide particle is 1 nm or moreand 50 nm or less.
 29. The oxide particles according to claim 27,wherein the silicon compound comprises amorphous silicon oxide.